Vulnerability-Lookup

CVE-2026-93164 (GCVE-0-2026-93164)

Vulnerability from cvelistv5 – Published: 2026-09-17 16:11 – Updated: 2026-09-17 16:11

Title

uprobes/x86: Move optimized uprobe from nop5 to nop10

Summary

In the Linux kernel, the following vulnerability has been resolved: uprobes/x86: Move optimized uprobe from nop5 to nop10 Andrii reported an issue with optimized uprobes [1] that can clobber redzone area with call instruction storing return address on stack where user code may keep temporary data without adjusting rsp. Fixing this by moving the optimized uprobes on top of 10-bytes nop instruction, so we can squeeze another instruction to escape the redzone area before doing the call, like: lea -0x80(%rsp), %rsp call tramp Note the lea instruction is used to adjust the rsp register without changing the flags. We use nop10 and following transformation to optimized instructions above and back as suggested by Peterz [2]. Optimize path (int3_update_optimize): 1) Initial state after set_swbp() installed the uprobe: cc 2e 0f 1f 84 00 00 00 00 00 From offset 0 this is INT3 followed by the tail of the original 10-byte NOP. After a previous unoptimization bytes 5..9 may still contain the old call instruction, which remains valid for threads already there. 2) Rewrite the LEA tail and call displacement: cc [8d 64 24 80 e8 d0 d1 d2 d3] From offset 0 this traps on the uprobe INT3. Bytes 1..9 are not executable entry points while byte 0 is trapped. 3) Publish the first LEA byte: [48] 8d 64 24 80 e8 d0 d1 d2 d3 From offset 0 this is: lea -0x80(%rsp), %rsp call <uprobe-trampoline> Unoptimize path (int3_update_unoptimize): 1) Initial optimized state: 48 8d 64 24 80 e8 d0 d1 d2 d3 Same as 3) above. 2) Trap new entries before restoring the NOP bytes: [cc] 8d 64 24 80 e8 d0 d1 d2 d3 From offset 0 this traps. A thread that had already executed the LEA can still reach the intact CALL at offset 5. 3) Restore bytes 1..4 of the original NOP while keeping byte 0 trapped and byte 5 as CALL. cc [2e 0f 1f 84] e8 d0 d1 d2 d3 From offset 0 this still traps. Offset 5 is still the CALL for any thread that was already past the first LEA byte. 4) Publish the first byte of the original NOP: [66] 2e 0f 1f 84 e8 d0 d1 d2 d3 From offset 0 this is the restored 10-byte NOP; the CALL opcode and displacement are now only NOP operands. Offset 5 still decodes as CALL for a thread that was already there. Tthere is only a single target uprobe-trampoline for the given nop10 instruction address, so the CALL instruction will not be changed across unoptimization/optimization cycles. Therefore, any task that is preempted at the CALL instruction is guaranteed to observe that CALL and not anything else. Note as explained in [2] we need to use following nop10: PF1 PF2 ESC NOPL MOD SIB DISP32 NOP10: 0x66, 0x2e, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00 -- cs nopw 0x00000000(%rax,%rax,1) which means we need to allow 0x2e prefix which maps to INAT_PFX_CS attribute in is_prefix_bad function. Also changing the uprobe syscall error when called out of uprobe trampoline to -EPROTO, so we are able to detect the fixed kernel. The optimized uprobe performance stays the same: uprobe-nop : 3.129 ± 0.013M/s uprobe-push : 3.045 ± 0.006M/s uprobe-ret : 1.095 ± 0.004M/s --> uprobe-nop10 : 7.170 ± 0.020M/s uretprobe-nop : 2.143 ± 0.021M/s uretprobe-push : 2.090 ± 0.000M/s uretprobe-ret : 0.942 ± 0.000M/s --> uretprobe-nop10: 3.381 ± 0.003M/s usdt-nop : 3.245 ± 0.004M/s --> usdt-nop10 : 7.256 ± 0.023M/s [1] https://lore.kernel.org/bpf/20260509003146.976844-1-andrii@kernel.org/ [2] https://lore.kernel.org/bpf/20260518104306.GU3102624@noisy.programming.kicks-ass.net/#t

Severity

No CVSS data available.

Assigner

Linux mitre root

References

2 references

URL	Tags
https://git.kernel.org/stable/c/1b3fecd0991004066…
https://git.kernel.org/stable/c/554ba38456dad8053…

Impacted products

2 products

Vendor	Product	Version	CPE status
Linux	Linux	Affected: ba2bfc97b4629b10bd8d02b36e04f3932a04cac4 , < 1b3fecd09910040668b752f3377d7218ca5c59ac (git) Affected: ba2bfc97b4629b10bd8d02b36e04f3932a04cac4 , < 554ba38456dad8053a1a80afe6ae6da9eff745cc (git)	guessed
Linux	Linux	Affected: 6.18 Unaffected: 0 , < 6.18 (semver) Unaffected: 7.2.6 , ≤ 7.2.* (semver) Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)	guessed

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/x86/kernel/uprobes.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "1b3fecd09910040668b752f3377d7218ca5c59ac",
              "status": "affected",
              "version": "ba2bfc97b4629b10bd8d02b36e04f3932a04cac4",
              "versionType": "git"
            },
            {
              "lessThan": "554ba38456dad8053a1a80afe6ae6da9eff745cc",
              "status": "affected",
              "version": "ba2bfc97b4629b10bd8d02b36e04f3932a04cac4",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "arch/x86/kernel/uprobes.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.18"
            },
            {
              "lessThan": "6.18",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.6",
                  "versionStartIncluding": "6.18",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3-rc1",
                  "versionStartIncluding": "6.18",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nuprobes/x86: Move optimized uprobe from nop5 to nop10\n\nAndrii reported an issue with optimized uprobes [1] that can clobber\nredzone area with call instruction storing return address on stack\nwhere user code may keep temporary data without adjusting rsp.\n\nFixing this by moving the optimized uprobes on top of 10-bytes nop\ninstruction, so we can squeeze another instruction to escape the\nredzone area before doing the call, like:\n\n  lea -0x80(%rsp), %rsp\n  call tramp\n\nNote the lea instruction is used to adjust the rsp register without\nchanging the flags.\n\nWe use nop10 and following transformation to optimized instructions\nabove and back as suggested by Peterz [2].\n\nOptimize path (int3_update_optimize):\n\n  1) Initial state after set_swbp() installed the uprobe:\n      cc 2e 0f 1f 84 00 00 00 00 00\n\n     From offset 0 this is INT3 followed by the tail of the original\n     10-byte NOP.\n\n     After a previous unoptimization bytes 5..9 may still contain the\n     old call instruction, which remains valid for threads already there.\n\n  2) Rewrite the LEA tail and call displacement:\n      cc [8d 64 24 80 e8 d0 d1 d2 d3]\n\n     From offset 0 this traps on the uprobe INT3.  Bytes 1..9 are not\n     executable entry points while byte 0 is trapped.\n\n  3) Publish the first LEA byte:\n      [48] 8d 64 24 80 e8 d0 d1 d2 d3\n\n     From offset 0 this is:\n        lea -0x80(%rsp), %rsp\n        call \u003cuprobe-trampoline\u003e\n\nUnoptimize path (int3_update_unoptimize):\n\n  1) Initial optimized state:\n      48 8d 64 24 80 e8 d0 d1 d2 d3\n     Same as 3) above.\n\n  2) Trap new entries before restoring the NOP bytes:\n      [cc] 8d 64 24 80 e8 d0 d1 d2 d3\n\n     From offset 0 this traps. A thread that had already executed the\n     LEA can still reach the intact CALL at offset 5.\n\n  3) Restore bytes 1..4 of the original NOP while keeping byte 0 trapped\n     and byte 5 as CALL.\n      cc [2e 0f 1f 84] e8 d0 d1 d2 d3\n\n     From offset 0 this still traps. Offset 5 is still the CALL for any\n     thread that was already past the first LEA byte.\n\n  4) Publish the first byte of the original NOP:\n      [66] 2e 0f 1f 84 e8 d0 d1 d2 d3\n\n     From offset 0 this is the restored 10-byte NOP; the CALL opcode and\n     displacement are now only NOP operands.  Offset 5 still decodes as\n     CALL for a thread that was already there.\n\n     Tthere is only a single target uprobe-trampoline for the given nop10\n     instruction address, so the CALL instruction will not be changed across\n     unoptimization/optimization cycles.\n     Therefore, any task that is preempted at the CALL instruction is guaranteed\n     to observe that CALL and not anything else.\n\nNote as explained in [2] we need to use following nop10:\n       PF1   PF2   ESC   NOPL  MOD   SIB   DISP32\nNOP10: 0x66, 0x2e, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00 -- cs nopw 0x00000000(%rax,%rax,1)\n\nwhich means we need to allow 0x2e prefix which maps to INAT_PFX_CS\nattribute in is_prefix_bad function.\n\nAlso changing the uprobe syscall error when called out of uprobe\ntrampoline to -EPROTO, so we are able to detect the fixed kernel.\n\nThe optimized uprobe performance stays the same:\n\n        uprobe-nop     :    3.129 \u00b1 0.013M/s\n        uprobe-push    :    3.045 \u00b1 0.006M/s\n        uprobe-ret     :    1.095 \u00b1 0.004M/s\n  --\u003e   uprobe-nop10   :    7.170 \u00b1 0.020M/s\n        uretprobe-nop  :    2.143 \u00b1 0.021M/s\n        uretprobe-push :    2.090 \u00b1 0.000M/s\n        uretprobe-ret  :    0.942 \u00b1 0.000M/s\n  --\u003e   uretprobe-nop10:    3.381 \u00b1 0.003M/s\n        usdt-nop       :    3.245 \u00b1 0.004M/s\n  --\u003e   usdt-nop10     :    7.256 \u00b1 0.023M/s\n\n[1] https://lore.kernel.org/bpf/20260509003146.976844-1-andrii@kernel.org/\n[2] https://lore.kernel.org/bpf/20260518104306.GU3102624@noisy.programming.kicks-ass.net/#t"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-17T16:11:57.248Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/1b3fecd09910040668b752f3377d7218ca5c59ac"
        },
        {
          "url": "https://git.kernel.org/stable/c/554ba38456dad8053a1a80afe6ae6da9eff745cc"
        }
      ],
      "title": "uprobes/x86: Move optimized uprobe from nop5 to nop10",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-93164",
    "datePublished": "2026-09-17T16:11:57.248Z",
    "dateReserved": "2026-09-17T16:02:15.090Z",
    "dateUpdated": "2026-09-17T16:11:57.248Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "defaultStatus": "unaffected",
                "product": "Linux",
                "programFiles": [
                  "arch/x86/kernel/uprobes.c"
                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux",
                "versions": [
                  {
                    "lessThan": "1b3fecd09910040668b752f3377d7218ca5c59ac",
                    "status": "affected",
                    "version": "ba2bfc97b4629b10bd8d02b36e04f3932a04cac4",
                    "versionType": "git"
                  },
                  {
                    "lessThan": "554ba38456dad8053a1a80afe6ae6da9eff745cc",
                    "status": "affected",
                    "version": "ba2bfc97b4629b10bd8d02b36e04f3932a04cac4",
                    "versionType": "git"
                  }
                ]
              },
              {
                "defaultStatus": "affected",
                "product": "Linux",
                "programFiles": [
                  "arch/x86/kernel/uprobes.c"
                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux",
                "versions": [
                  {
                    "status": "affected",
                    "version": "6.18"
                  },
                  {
                    "lessThan": "6.18",
                    "status": "unaffected",
                    "version": "0",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "7.2.*",
                    "status": "unaffected",
                    "version": "7.2.6",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "*",
                    "status": "unaffected",
                    "version": "7.3-rc1",
                    "versionType": "original_commit_for_fix"
                  }
                ]
              }
            ],
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nuprobes/x86: Move optimized uprobe from nop5 to nop10\n\nAndrii reported an issue with optimized uprobes [1] that can clobber\nredzone area with call instruction storing return address on stack\nwhere user code may keep temporary data without adjusting rsp.\n\nFixing this by moving the optimized uprobes on top of 10-bytes nop\ninstruction, so we can squeeze another instruction to escape the\nredzone area before doing the call, like:\n\n  lea -0x80(%rsp), %rsp\n  call tramp\n\nNote the lea instruction is used to adjust the rsp register without\nchanging the flags.\n\nWe use nop10 and following transformation to optimized instructions\nabove and back as suggested by Peterz [2].\n\nOptimize path (int3_update_optimize):\n\n  1) Initial state after set_swbp() installed the uprobe:\n      cc 2e 0f 1f 84 00 00 00 00 00\n\n     From offset 0 this is INT3 followed by the tail of the original\n     10-byte NOP.\n\n     After a previous unoptimization bytes 5..9 may still contain the\n     old call instruction, which remains valid for threads already there.\n\n  2) Rewrite the LEA tail and call displacement:\n      cc [8d 64 24 80 e8 d0 d1 d2 d3]\n\n     From offset 0 this traps on the uprobe INT3.  Bytes 1..9 are not\n     executable entry points while byte 0 is trapped.\n\n  3) Publish the first LEA byte:\n      [48] 8d 64 24 80 e8 d0 d1 d2 d3\n\n     From offset 0 this is:\n        lea -0x80(%rsp), %rsp\n        call \u003cuprobe-trampoline\u003e\n\nUnoptimize path (int3_update_unoptimize):\n\n  1) Initial optimized state:\n      48 8d 64 24 80 e8 d0 d1 d2 d3\n     Same as 3) above.\n\n  2) Trap new entries before restoring the NOP bytes:\n      [cc] 8d 64 24 80 e8 d0 d1 d2 d3\n\n     From offset 0 this traps. A thread that had already executed the\n     LEA can still reach the intact CALL at offset 5.\n\n  3) Restore bytes 1..4 of the original NOP while keeping byte 0 trapped\n     and byte 5 as CALL.\n      cc [2e 0f 1f 84] e8 d0 d1 d2 d3\n\n     From offset 0 this still traps. Offset 5 is still the CALL for any\n     thread that was already past the first LEA byte.\n\n  4) Publish the first byte of the original NOP:\n      [66] 2e 0f 1f 84 e8 d0 d1 d2 d3\n\n     From offset 0 this is the restored 10-byte NOP; the CALL opcode and\n     displacement are now only NOP operands.  Offset 5 still decodes as\n     CALL for a thread that was already there.\n\n     Tthere is only a single target uprobe-trampoline for the given nop10\n     instruction address, so the CALL instruction will not be changed across\n     unoptimization/optimization cycles.\n     Therefore, any task that is preempted at the CALL instruction is guaranteed\n     to observe that CALL and not anything else.\n\nNote as explained in [2] we need to use following nop10:\n       PF1   PF2   ESC   NOPL  MOD   SIB   DISP32\nNOP10: 0x66, 0x2e, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00 -- cs nopw 0x00000000(%rax,%rax,1)\n\nwhich means we need to allow 0x2e prefix which maps to INAT_PFX_CS\nattribute in is_prefix_bad function.\n\nAlso changing the uprobe syscall error when called out of uprobe\ntrampoline to -EPROTO, so we are able to detect the fixed kernel.\n\nThe optimized uprobe performance stays the same:\n\n        uprobe-nop     :    3.129 \u00b1 0.013M/s\n        uprobe-push    :    3.045 \u00b1 0.006M/s\n        uprobe-ret     :    1.095 \u00b1 0.004M/s\n  --\u003e   uprobe-nop10   :    7.170 \u00b1 0.020M/s\n        uretprobe-nop  :    2.143 \u00b1 0.021M/s\n        uretprobe-push :    2.090 \u00b1 0.000M/s\n        uretprobe-ret  :    0.942 \u00b1 0.000M/s\n  --\u003e   uretprobe-nop10:    3.381 \u00b1 0.003M/s\n        usdt-nop       :    3.245 \u00b1 0.004M/s\n  --\u003e   usdt-nop10     :    7.256 \u00b1 0.023M/s\n\n[1] https://lore.kernel.org/bpf/20260509003146.976844-1-andrii@kernel.org/\n[2] https://lore.kernel.org/bpf/20260518104306.GU3102624@noisy.programming.kicks-ass.net/#t"
          }
        ],
        "id": "CVE-2026-93164",
        "lastModified": "2026-09-17T17:18:11.890",
        "metrics": {},
        "published": "2026-09-17T17:18:11.890",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/1b3fecd09910040668b752f3377d7218ca5c59ac"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/554ba38456dad8053a1a80afe6ae6da9eff745cc"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    }
  }
}

FKIE_CVE-2026-93164

Vulnerability from fkie_nvd - Published: 2026-09-17 17:18 - Updated: 2026-09-17 17:18

Severity

Summary

References

	URL	Tags
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/1b3fecd09910040668b752f3377d7218ca5c59ac
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/554ba38456dad8053a1a80afe6ae6da9eff745cc

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/x86/kernel/uprobes.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "1b3fecd09910040668b752f3377d7218ca5c59ac",
              "status": "affected",
              "version": "ba2bfc97b4629b10bd8d02b36e04f3932a04cac4",
              "versionType": "git"
            },
            {
              "lessThan": "554ba38456dad8053a1a80afe6ae6da9eff745cc",
              "status": "affected",
              "version": "ba2bfc97b4629b10bd8d02b36e04f3932a04cac4",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "arch/x86/kernel/uprobes.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.18"
            },
            {
              "lessThan": "6.18",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nuprobes/x86: Move optimized uprobe from nop5 to nop10\n\nAndrii reported an issue with optimized uprobes [1] that can clobber\nredzone area with call instruction storing return address on stack\nwhere user code may keep temporary data without adjusting rsp.\n\nFixing this by moving the optimized uprobes on top of 10-bytes nop\ninstruction, so we can squeeze another instruction to escape the\nredzone area before doing the call, like:\n\n  lea -0x80(%rsp), %rsp\n  call tramp\n\nNote the lea instruction is used to adjust the rsp register without\nchanging the flags.\n\nWe use nop10 and following transformation to optimized instructions\nabove and back as suggested by Peterz [2].\n\nOptimize path (int3_update_optimize):\n\n  1) Initial state after set_swbp() installed the uprobe:\n      cc 2e 0f 1f 84 00 00 00 00 00\n\n     From offset 0 this is INT3 followed by the tail of the original\n     10-byte NOP.\n\n     After a previous unoptimization bytes 5..9 may still contain the\n     old call instruction, which remains valid for threads already there.\n\n  2) Rewrite the LEA tail and call displacement:\n      cc [8d 64 24 80 e8 d0 d1 d2 d3]\n\n     From offset 0 this traps on the uprobe INT3.  Bytes 1..9 are not\n     executable entry points while byte 0 is trapped.\n\n  3) Publish the first LEA byte:\n      [48] 8d 64 24 80 e8 d0 d1 d2 d3\n\n     From offset 0 this is:\n        lea -0x80(%rsp), %rsp\n        call \u003cuprobe-trampoline\u003e\n\nUnoptimize path (int3_update_unoptimize):\n\n  1) Initial optimized state:\n      48 8d 64 24 80 e8 d0 d1 d2 d3\n     Same as 3) above.\n\n  2) Trap new entries before restoring the NOP bytes:\n      [cc] 8d 64 24 80 e8 d0 d1 d2 d3\n\n     From offset 0 this traps. A thread that had already executed the\n     LEA can still reach the intact CALL at offset 5.\n\n  3) Restore bytes 1..4 of the original NOP while keeping byte 0 trapped\n     and byte 5 as CALL.\n      cc [2e 0f 1f 84] e8 d0 d1 d2 d3\n\n     From offset 0 this still traps. Offset 5 is still the CALL for any\n     thread that was already past the first LEA byte.\n\n  4) Publish the first byte of the original NOP:\n      [66] 2e 0f 1f 84 e8 d0 d1 d2 d3\n\n     From offset 0 this is the restored 10-byte NOP; the CALL opcode and\n     displacement are now only NOP operands.  Offset 5 still decodes as\n     CALL for a thread that was already there.\n\n     Tthere is only a single target uprobe-trampoline for the given nop10\n     instruction address, so the CALL instruction will not be changed across\n     unoptimization/optimization cycles.\n     Therefore, any task that is preempted at the CALL instruction is guaranteed\n     to observe that CALL and not anything else.\n\nNote as explained in [2] we need to use following nop10:\n       PF1   PF2   ESC   NOPL  MOD   SIB   DISP32\nNOP10: 0x66, 0x2e, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00 -- cs nopw 0x00000000(%rax,%rax,1)\n\nwhich means we need to allow 0x2e prefix which maps to INAT_PFX_CS\nattribute in is_prefix_bad function.\n\nAlso changing the uprobe syscall error when called out of uprobe\ntrampoline to -EPROTO, so we are able to detect the fixed kernel.\n\nThe optimized uprobe performance stays the same:\n\n        uprobe-nop     :    3.129 \u00b1 0.013M/s\n        uprobe-push    :    3.045 \u00b1 0.006M/s\n        uprobe-ret     :    1.095 \u00b1 0.004M/s\n  --\u003e   uprobe-nop10   :    7.170 \u00b1 0.020M/s\n        uretprobe-nop  :    2.143 \u00b1 0.021M/s\n        uretprobe-push :    2.090 \u00b1 0.000M/s\n        uretprobe-ret  :    0.942 \u00b1 0.000M/s\n  --\u003e   uretprobe-nop10:    3.381 \u00b1 0.003M/s\n        usdt-nop       :    3.245 \u00b1 0.004M/s\n  --\u003e   usdt-nop10     :    7.256 \u00b1 0.023M/s\n\n[1] https://lore.kernel.org/bpf/20260509003146.976844-1-andrii@kernel.org/\n[2] https://lore.kernel.org/bpf/20260518104306.GU3102624@noisy.programming.kicks-ass.net/#t"
    }
  ],
  "id": "CVE-2026-93164",
  "lastModified": "2026-09-17T17:18:11.890",
  "metrics": {},
  "published": "2026-09-17T17:18:11.890",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/1b3fecd09910040668b752f3377d7218ca5c59ac"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/554ba38456dad8053a1a80afe6ae6da9eff745cc"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}

GHSA-R7C2-7RH7-H943

Vulnerability from github – Published: 2026-09-17 18:32 – Updated: 2026-09-17 18:32

Details

In the Linux kernel, the following vulnerability has been resolved:

uprobes/x86: Move optimized uprobe from nop5 to nop10

Andrii reported an issue with optimized uprobes [1] that can clobber redzone area with call instruction storing return address on stack where user code may keep temporary data without adjusting rsp.

Fixing this by moving the optimized uprobes on top of 10-bytes nop instruction, so we can squeeze another instruction to escape the redzone area before doing the call, like:

lea -0x80(%rsp), %rsp call tramp

Note the lea instruction is used to adjust the rsp register without changing the flags.

We use nop10 and following transformation to optimized instructions above and back as suggested by Peterz [2].

Optimize path (int3_update_optimize):

1) Initial state after set_swbp() installed the uprobe: cc 2e 0f 1f 84 00 00 00 00 00

 From offset 0 this is INT3 followed by the tail of the original
 10-byte NOP.

 After a previous unoptimization bytes 5..9 may still contain the
 old call instruction, which remains valid for threads already there.

2) Rewrite the LEA tail and call displacement: cc [8d 64 24 80 e8 d0 d1 d2 d3]

 From offset 0 this traps on the uprobe INT3.  Bytes 1..9 are not
 executable entry points while byte 0 is trapped.

3) Publish the first LEA byte: [48] 8d 64 24 80 e8 d0 d1 d2 d3

 From offset 0 this is:
    lea -0x80(%rsp), %rsp
    call <uprobe-trampoline>

Unoptimize path (int3_update_unoptimize):

1) Initial optimized state: 48 8d 64 24 80 e8 d0 d1 d2 d3 Same as 3) above.

2) Trap new entries before restoring the NOP bytes: [cc] 8d 64 24 80 e8 d0 d1 d2 d3

 From offset 0 this traps. A thread that had already executed the
 LEA can still reach the intact CALL at offset 5.

3) Restore bytes 1..4 of the original NOP while keeping byte 0 trapped and byte 5 as CALL. cc [2e 0f 1f 84] e8 d0 d1 d2 d3

 From offset 0 this still traps. Offset 5 is still the CALL for any
 thread that was already past the first LEA byte.

4) Publish the first byte of the original NOP: [66] 2e 0f 1f 84 e8 d0 d1 d2 d3

 From offset 0 this is the restored 10-byte NOP; the CALL opcode and
 displacement are now only NOP operands.  Offset 5 still decodes as
 CALL for a thread that was already there.

 Tthere is only a single target uprobe-trampoline for the given nop10
 instruction address, so the CALL instruction will not be changed across
 unoptimization/optimization cycles.
 Therefore, any task that is preempted at the CALL instruction is guaranteed
 to observe that CALL and not anything else.

Note as explained in [2] we need to use following nop10: PF1 PF2 ESC NOPL MOD SIB DISP32 NOP10: 0x66, 0x2e, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00 -- cs nopw 0x00000000(%rax,%rax,1)

which means we need to allow 0x2e prefix which maps to INAT_PFX_CS attribute in is_prefix_bad function.

Also changing the uprobe syscall error when called out of uprobe trampoline to -EPROTO, so we are able to detect the fixed kernel.

The optimized uprobe performance stays the same:

    uprobe-nop     :    3.129 ± 0.013M/s
    uprobe-push    :    3.045 ± 0.006M/s
    uprobe-ret     :    1.095 ± 0.004M/s

--> uprobe-nop10 : 7.170 ± 0.020M/s uretprobe-nop : 2.143 ± 0.021M/s uretprobe-push : 2.090 ± 0.000M/s uretprobe-ret : 0.942 ± 0.000M/s --> uretprobe-nop10: 3.381 ± 0.003M/s usdt-nop : 3.245 ± 0.004M/s --> usdt-nop10 : 7.256 ± 0.023M/s

[1] https://lore.kernel.org/bpf/20260509003146.976844-1-andrii@kernel.org/ [2] https://lore.kernel.org/bpf/20260518104306.GU3102624@noisy.programming.kicks-ass.net/#t

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-93164"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-17T17:18:11Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nuprobes/x86: Move optimized uprobe from nop5 to nop10\n\nAndrii reported an issue with optimized uprobes [1] that can clobber\nredzone area with call instruction storing return address on stack\nwhere user code may keep temporary data without adjusting rsp.\n\nFixing this by moving the optimized uprobes on top of 10-bytes nop\ninstruction, so we can squeeze another instruction to escape the\nredzone area before doing the call, like:\n\n  lea -0x80(%rsp), %rsp\n  call tramp\n\nNote the lea instruction is used to adjust the rsp register without\nchanging the flags.\n\nWe use nop10 and following transformation to optimized instructions\nabove and back as suggested by Peterz [2].\n\nOptimize path (int3_update_optimize):\n\n  1) Initial state after set_swbp() installed the uprobe:\n      cc 2e 0f 1f 84 00 00 00 00 00\n\n     From offset 0 this is INT3 followed by the tail of the original\n     10-byte NOP.\n\n     After a previous unoptimization bytes 5..9 may still contain the\n     old call instruction, which remains valid for threads already there.\n\n  2) Rewrite the LEA tail and call displacement:\n      cc [8d 64 24 80 e8 d0 d1 d2 d3]\n\n     From offset 0 this traps on the uprobe INT3.  Bytes 1..9 are not\n     executable entry points while byte 0 is trapped.\n\n  3) Publish the first LEA byte:\n      [48] 8d 64 24 80 e8 d0 d1 d2 d3\n\n     From offset 0 this is:\n        lea -0x80(%rsp), %rsp\n        call \u003cuprobe-trampoline\u003e\n\nUnoptimize path (int3_update_unoptimize):\n\n  1) Initial optimized state:\n      48 8d 64 24 80 e8 d0 d1 d2 d3\n     Same as 3) above.\n\n  2) Trap new entries before restoring the NOP bytes:\n      [cc] 8d 64 24 80 e8 d0 d1 d2 d3\n\n     From offset 0 this traps. A thread that had already executed the\n     LEA can still reach the intact CALL at offset 5.\n\n  3) Restore bytes 1..4 of the original NOP while keeping byte 0 trapped\n     and byte 5 as CALL.\n      cc [2e 0f 1f 84] e8 d0 d1 d2 d3\n\n     From offset 0 this still traps. Offset 5 is still the CALL for any\n     thread that was already past the first LEA byte.\n\n  4) Publish the first byte of the original NOP:\n      [66] 2e 0f 1f 84 e8 d0 d1 d2 d3\n\n     From offset 0 this is the restored 10-byte NOP; the CALL opcode and\n     displacement are now only NOP operands.  Offset 5 still decodes as\n     CALL for a thread that was already there.\n\n     Tthere is only a single target uprobe-trampoline for the given nop10\n     instruction address, so the CALL instruction will not be changed across\n     unoptimization/optimization cycles.\n     Therefore, any task that is preempted at the CALL instruction is guaranteed\n     to observe that CALL and not anything else.\n\nNote as explained in [2] we need to use following nop10:\n       PF1   PF2   ESC   NOPL  MOD   SIB   DISP32\nNOP10: 0x66, 0x2e, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00 -- cs nopw 0x00000000(%rax,%rax,1)\n\nwhich means we need to allow 0x2e prefix which maps to INAT_PFX_CS\nattribute in is_prefix_bad function.\n\nAlso changing the uprobe syscall error when called out of uprobe\ntrampoline to -EPROTO, so we are able to detect the fixed kernel.\n\nThe optimized uprobe performance stays the same:\n\n        uprobe-nop     :    3.129 \u00b1 0.013M/s\n        uprobe-push    :    3.045 \u00b1 0.006M/s\n        uprobe-ret     :    1.095 \u00b1 0.004M/s\n  --\u003e   uprobe-nop10   :    7.170 \u00b1 0.020M/s\n        uretprobe-nop  :    2.143 \u00b1 0.021M/s\n        uretprobe-push :    2.090 \u00b1 0.000M/s\n        uretprobe-ret  :    0.942 \u00b1 0.000M/s\n  --\u003e   uretprobe-nop10:    3.381 \u00b1 0.003M/s\n        usdt-nop       :    3.245 \u00b1 0.004M/s\n  --\u003e   usdt-nop10     :    7.256 \u00b1 0.023M/s\n\n[1] https://lore.kernel.org/bpf/20260509003146.976844-1-andrii@kernel.org/\n[2] https://lore.kernel.org/bpf/20260518104306.GU3102624@noisy.programming.kicks-ass.net/#t",
  "id": "GHSA-r7c2-7rh7-h943",
  "modified": "2026-09-17T18:32:12Z",
  "published": "2026-09-17T18:32:12Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-93164"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1b3fecd09910040668b752f3377d7218ca5c59ac"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/554ba38456dad8053a1a80afe6ae6da9eff745cc"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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Action not permitted

CVE-2026-93164 (GCVE-0-2026-93164)

FKIE_CVE-2026-93164

GHSA-R7C2-7RH7-H943

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