Vulnerability-Lookup

CVE-2026-89541 (GCVE-0-2026-89541)

Vulnerability from cvelistv5 – Published: 2026-09-11 19:44 – Updated: 2026-09-13 06:30

Title

SUNRPC: harden gss_unwrap_resp_priv length checks

Summary

In the Linux kernel, the following vulnerability has been resolved: SUNRPC: harden gss_unwrap_resp_priv length checks gss_unwrap_resp_priv() validates the RPCSEC_GSS opaque length with offset = (u8 *)(p) - (u8 *)head->iov_base; if (offset + opaque_len > rcv_buf->len) goto unwrap_failed; maj_stat = gss_unwrap(ctx->gc_gss_ctx, offset, offset + opaque_len, rcv_buf); Both operands are u32 and the sum is computed in u32. A reply with opaque_len near 0xffffffff makes offset + opaque_len wrap to a small value that is below rcv_buf->len, so the bound check passes and gss_unwrap() is called with end < begin. The check also lacks a lower bound, so any opaque_len in [0, GSS_KRB5_TOK_HDR_LEN) is accepted and forwarded to gss_krb5_unwrap_v2(), whose pre-decrypt header reads at ptr+4 and ptr+6 then run past the token. A krb5p NFS server returning a crafted RPCSEC_GSS reply can drive the client into out-of-bounds reads in gss_krb5_unwrap_v2() and the rotate_left() loop that follows. Fix by replacing the single combined check with three guards that are safe in u32 arithmetic and that enforce the RFC 4121 minimum outer token length: if (offset > rcv_buf->len) goto unwrap_failed; if (opaque_len > rcv_buf->len - offset) goto unwrap_failed; if (opaque_len < GSS_KRB5_TOK_HDR_LEN) goto unwrap_failed; The first guard makes the subtraction in the second guard unconditionally safe; offset is derived from a successful xdr_inline_decode() in the head kvec, so in practice it already satisfies the bound. The floor mirrors the server-side check added in commit 5b757c2e57a5 ("SUNRPC: svcauth_gss: enforce krb5 token minimum length").

Severity

9.8 (Critical)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Assigner

Linux mitre root

References

4 references

URL	Tags
https://git.kernel.org/stable/c/89a15a50f84d32d4b…
https://git.kernel.org/stable/c/ebcbd2523a8524c3d…
https://git.kernel.org/stable/c/d395c30d570ca6168…
https://git.kernel.org/stable/c/87831b92112c81db2…

Impacted products

2 products

Vendor	Product	Version	CPE status
Linux	Linux	Affected: 2d2da60c63b67174add32f06e8d54c3a0c5cd9cf , < 89a15a50f84d32d4b99db86f957427fcbe20a99a (git) Affected: 2d2da60c63b67174add32f06e8d54c3a0c5cd9cf , < ebcbd2523a8524c3d24e111cdbed8e271d910269 (git) Affected: 2d2da60c63b67174add32f06e8d54c3a0c5cd9cf , < d395c30d570ca6168f0297b191709927d1258273 (git) Affected: 2d2da60c63b67174add32f06e8d54c3a0c5cd9cf , < 87831b92112c81db251d46756d65daa4f91af6a2 (git)	guessed
Linux	Linux	Affected: 2.6.15 Unaffected: 0 , < 2.6.15 (semver) Unaffected: 6.12.109 , ≤ 6.12.* (semver) Unaffected: 6.18.50 , ≤ 6.18.* (semver) Unaffected: 7.2.4 , ≤ 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": [
            "net/sunrpc/auth_gss/auth_gss.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "89a15a50f84d32d4b99db86f957427fcbe20a99a",
              "status": "affected",
              "version": "2d2da60c63b67174add32f06e8d54c3a0c5cd9cf",
              "versionType": "git"
            },
            {
              "lessThan": "ebcbd2523a8524c3d24e111cdbed8e271d910269",
              "status": "affected",
              "version": "2d2da60c63b67174add32f06e8d54c3a0c5cd9cf",
              "versionType": "git"
            },
            {
              "lessThan": "d395c30d570ca6168f0297b191709927d1258273",
              "status": "affected",
              "version": "2d2da60c63b67174add32f06e8d54c3a0c5cd9cf",
              "versionType": "git"
            },
            {
              "lessThan": "87831b92112c81db251d46756d65daa4f91af6a2",
              "status": "affected",
              "version": "2d2da60c63b67174add32f06e8d54c3a0c5cd9cf",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/sunrpc/auth_gss/auth_gss.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.15"
            },
            {
              "lessThan": "2.6.15",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.109",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "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": "6.12.109",
                  "versionStartIncluding": "2.6.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.50",
                  "versionStartIncluding": "2.6.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.4",
                  "versionStartIncluding": "2.6.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3-rc1",
                  "versionStartIncluding": "2.6.15",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: harden gss_unwrap_resp_priv length checks\n\ngss_unwrap_resp_priv() validates the RPCSEC_GSS opaque length with\n\n    offset = (u8 *)(p) - (u8 *)head-\u003eiov_base;\n    if (offset + opaque_len \u003e rcv_buf-\u003elen)\n            goto unwrap_failed;\n    maj_stat = gss_unwrap(ctx-\u003egc_gss_ctx, offset,\n                          offset + opaque_len, rcv_buf);\n\nBoth operands are u32 and the sum is computed in u32. A reply with\nopaque_len near 0xffffffff makes offset + opaque_len wrap to a small\nvalue that is below rcv_buf-\u003elen, so the bound check passes and\ngss_unwrap() is called with end \u003c begin. The check also lacks a\nlower bound, so any opaque_len in [0, GSS_KRB5_TOK_HDR_LEN) is\naccepted and forwarded to gss_krb5_unwrap_v2(), whose pre-decrypt\nheader reads at ptr+4 and ptr+6 then run past the token.\n\nA krb5p NFS server returning a crafted RPCSEC_GSS reply can drive\nthe client into out-of-bounds reads in gss_krb5_unwrap_v2() and the\nrotate_left() loop that follows.\n\nFix by replacing the single combined check with three guards that\nare safe in u32 arithmetic and that enforce the RFC 4121 minimum\nouter token length:\n\n    if (offset \u003e rcv_buf-\u003elen)\n            goto unwrap_failed;\n    if (opaque_len \u003e rcv_buf-\u003elen - offset)\n            goto unwrap_failed;\n    if (opaque_len \u003c GSS_KRB5_TOK_HDR_LEN)\n            goto unwrap_failed;\n\nThe first guard makes the subtraction in the second guard\nunconditionally safe; offset is derived from a successful\nxdr_inline_decode() in the head kvec, so in practice it already\nsatisfies the bound. The floor mirrors the server-side check added\nin commit 5b757c2e57a5 (\"SUNRPC: svcauth_gss: enforce krb5 token\nminimum length\")."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - gss_unwrap_resp_priv() runs in the Linux NFS/SUNRPC client while decoding RPCSEC_GSS privacy (krb5p) replies; a malicious or compromised NFS server supplies the crafted opaque_len and wrap token over the existing TCP/UDP/RDMA RPC connection.\nAC:L - The attacker fully controls the reply, including opaque_len and the cleartext RFC 4121 header, and a single response can make offset+opaque_len wrap in u32 or fall below GSS_KRB5_TOK_HDR_LEN; no race or layout beyond the attacker\u2019s control is required.\nPR:N - The attacker is the remote RPC/NFS peer that already holds the GSS session keys needed to pass gss_validate(); no local account, user namespace, or capability on the victim client is required.\nUI:N - Once a krb5p NFS mount or other SUNRPC GSS-privacy client is already in use, normal client RPCs elicit replies the attacker can craft; no extra victim action is needed at attack time.\nS:U - Out-of-bounds reads, rotate/decrypt memory corruption, and crashes stay inside the victim kernel\u2019s SUNRPC client and do not cross a VM, IOMMU, or other security-authority boundary.\nC:H - A short or wrapped opaque_len makes gss_krb5_unwrap_v2() read past the token at ptr+4/ptr+6 and feeds rotate_left()/decrypt with wrapped lengths, disclosing adjacent kernel memory; unwrap cleanup can also memmove nearly UINT_MAX bytes.\nI:H - The same wrapped lengths drive rotate_left() writes, CBC/AEAD decrypt over an unbounded xdr subsegment (xdr_buf_subsegment\u2019s error is ignored), and gss_krb5_unwrap_v2()\u2019s unsigned movelen underflow into a near-4GiB memmove, enabling kernel memory corruption.\nA:H - rotate_left() can divide-by-zero on a zero-length subbuffer, spin in a multi-gigabyte kernel loop on a wrapped subsegment, or oops/panic on the huge memmove or out-of-bounds header access."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-13T06:30:40.442Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/89a15a50f84d32d4b99db86f957427fcbe20a99a"
        },
        {
          "url": "https://git.kernel.org/stable/c/ebcbd2523a8524c3d24e111cdbed8e271d910269"
        },
        {
          "url": "https://git.kernel.org/stable/c/d395c30d570ca6168f0297b191709927d1258273"
        },
        {
          "url": "https://git.kernel.org/stable/c/87831b92112c81db251d46756d65daa4f91af6a2"
        }
      ],
      "title": "SUNRPC: harden gss_unwrap_resp_priv length checks",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89541",
    "datePublished": "2026-09-11T19:44:18.188Z",
    "dateReserved": "2026-09-11T19:38:34.721Z",
    "dateUpdated": "2026-09-13T06:30:40.442Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-89541",
      "date": "2026-09-12",
      "epss": "0.00168",
      "percentile": "0.06338"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-89541\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-09-11T20:19:37.247\",\"lastModified\":\"2026-09-13T07:17:16.397\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nSUNRPC: harden gss_unwrap_resp_priv length checks\\n\\ngss_unwrap_resp_priv() validates the RPCSEC_GSS opaque length with\\n\\n    offset = (u8 *)(p) - (u8 *)head-\u003eiov_base;\\n    if (offset + opaque_len \u003e rcv_buf-\u003elen)\\n            goto unwrap_failed;\\n    maj_stat = gss_unwrap(ctx-\u003egc_gss_ctx, offset,\\n                          offset + opaque_len, rcv_buf);\\n\\nBoth operands are u32 and the sum is computed in u32. A reply with\\nopaque_len near 0xffffffff makes offset + opaque_len wrap to a small\\nvalue that is below rcv_buf-\u003elen, so the bound check passes and\\ngss_unwrap() is called with end \u003c begin. The check also lacks a\\nlower bound, so any opaque_len in [0, GSS_KRB5_TOK_HDR_LEN) is\\naccepted and forwarded to gss_krb5_unwrap_v2(), whose pre-decrypt\\nheader reads at ptr+4 and ptr+6 then run past the token.\\n\\nA krb5p NFS server returning a crafted RPCSEC_GSS reply can drive\\nthe client into out-of-bounds reads in gss_krb5_unwrap_v2() and the\\nrotate_left() loop that follows.\\n\\nFix by replacing the single combined check with three guards that\\nare safe in u32 arithmetic and that enforce the RFC 4121 minimum\\nouter token length:\\n\\n    if (offset \u003e rcv_buf-\u003elen)\\n            goto unwrap_failed;\\n    if (opaque_len \u003e rcv_buf-\u003elen - offset)\\n            goto unwrap_failed;\\n    if (opaque_len \u003c GSS_KRB5_TOK_HDR_LEN)\\n            goto unwrap_failed;\\n\\nThe first guard makes the subtraction in the second guard\\nunconditionally safe; offset is derived from a successful\\nxdr_inline_decode() in the head kvec, so in practice it already\\nsatisfies the bound. The floor mirrors the server-side check added\\nin commit 5b757c2e57a5 (\\\"SUNRPC: svcauth_gss: enforce krb5 token\\nminimum length\\\").\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"net/sunrpc/auth_gss/auth_gss.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"2d2da60c63b67174add32f06e8d54c3a0c5cd9cf\",\"lessThan\":\"89a15a50f84d32d4b99db86f957427fcbe20a99a\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"2d2da60c63b67174add32f06e8d54c3a0c5cd9cf\",\"lessThan\":\"ebcbd2523a8524c3d24e111cdbed8e271d910269\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"2d2da60c63b67174add32f06e8d54c3a0c5cd9cf\",\"lessThan\":\"d395c30d570ca6168f0297b191709927d1258273\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"2d2da60c63b67174add32f06e8d54c3a0c5cd9cf\",\"lessThan\":\"87831b92112c81db251d46756d65daa4f91af6a2\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"net/sunrpc/auth_gss/auth_gss.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"2.6.15\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"2.6.15\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.109\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.50\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2.4\",\"lessThanOrEqual\":\"7.2.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.3-rc1\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":9.8,\"baseSeverity\":\"CRITICAL\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":3.9,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/87831b92112c81db251d46756d65daa4f91af6a2\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/89a15a50f84d32d4b99db86f957427fcbe20a99a\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/d395c30d570ca6168f0297b191709927d1258273\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/ebcbd2523a8524c3d24e111cdbed8e271d910269\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-09-13T06:50:09+00:00",
      "cve": "CVE-2026-89541",
      "id": "CVE-2026-89541",
      "initial_release_date": "2026-09-11T19:44:18.188000+00:00",
      "product_status:known_affected": "2",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: Linux kernel (SUNRPC): Out-of-bounds read via crafted RPCSEC_GSS reply",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89541.json",
      "version": "3"
    }
  }
}

FKIE_CVE-2026-89541

Vulnerability from fkie_nvd - Published: 2026-09-11 20:19 - Updated: 2026-09-13 07:17

Severity

9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Summary

References

	URL	Tags
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/87831b92112c81db251d46756d65daa4f91af6a2
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/89a15a50f84d32d4b99db86f957427fcbe20a99a
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/d395c30d570ca6168f0297b191709927d1258273
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/ebcbd2523a8524c3d24e111cdbed8e271d910269

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/sunrpc/auth_gss/auth_gss.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "89a15a50f84d32d4b99db86f957427fcbe20a99a",
              "status": "affected",
              "version": "2d2da60c63b67174add32f06e8d54c3a0c5cd9cf",
              "versionType": "git"
            },
            {
              "lessThan": "ebcbd2523a8524c3d24e111cdbed8e271d910269",
              "status": "affected",
              "version": "2d2da60c63b67174add32f06e8d54c3a0c5cd9cf",
              "versionType": "git"
            },
            {
              "lessThan": "d395c30d570ca6168f0297b191709927d1258273",
              "status": "affected",
              "version": "2d2da60c63b67174add32f06e8d54c3a0c5cd9cf",
              "versionType": "git"
            },
            {
              "lessThan": "87831b92112c81db251d46756d65daa4f91af6a2",
              "status": "affected",
              "version": "2d2da60c63b67174add32f06e8d54c3a0c5cd9cf",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/sunrpc/auth_gss/auth_gss.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.15"
            },
            {
              "lessThan": "2.6.15",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.109",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "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\nSUNRPC: harden gss_unwrap_resp_priv length checks\n\ngss_unwrap_resp_priv() validates the RPCSEC_GSS opaque length with\n\n    offset = (u8 *)(p) - (u8 *)head-\u003eiov_base;\n    if (offset + opaque_len \u003e rcv_buf-\u003elen)\n            goto unwrap_failed;\n    maj_stat = gss_unwrap(ctx-\u003egc_gss_ctx, offset,\n                          offset + opaque_len, rcv_buf);\n\nBoth operands are u32 and the sum is computed in u32. A reply with\nopaque_len near 0xffffffff makes offset + opaque_len wrap to a small\nvalue that is below rcv_buf-\u003elen, so the bound check passes and\ngss_unwrap() is called with end \u003c begin. The check also lacks a\nlower bound, so any opaque_len in [0, GSS_KRB5_TOK_HDR_LEN) is\naccepted and forwarded to gss_krb5_unwrap_v2(), whose pre-decrypt\nheader reads at ptr+4 and ptr+6 then run past the token.\n\nA krb5p NFS server returning a crafted RPCSEC_GSS reply can drive\nthe client into out-of-bounds reads in gss_krb5_unwrap_v2() and the\nrotate_left() loop that follows.\n\nFix by replacing the single combined check with three guards that\nare safe in u32 arithmetic and that enforce the RFC 4121 minimum\nouter token length:\n\n    if (offset \u003e rcv_buf-\u003elen)\n            goto unwrap_failed;\n    if (opaque_len \u003e rcv_buf-\u003elen - offset)\n            goto unwrap_failed;\n    if (opaque_len \u003c GSS_KRB5_TOK_HDR_LEN)\n            goto unwrap_failed;\n\nThe first guard makes the subtraction in the second guard\nunconditionally safe; offset is derived from a successful\nxdr_inline_decode() in the head kvec, so in practice it already\nsatisfies the bound. The floor mirrors the server-side check added\nin commit 5b757c2e57a5 (\"SUNRPC: svcauth_gss: enforce krb5 token\nminimum length\")."
    }
  ],
  "id": "CVE-2026-89541",
  "lastModified": "2026-09-13T07:17:16.397",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-09-11T20:19:37.247",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/87831b92112c81db251d46756d65daa4f91af6a2"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/89a15a50f84d32d4b99db86f957427fcbe20a99a"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d395c30d570ca6168f0297b191709927d1258273"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/ebcbd2523a8524c3d24e111cdbed8e271d910269"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}

GHSA-8H82-J8R3-JR82

Vulnerability from github – Published: 2026-09-11 21:31 – Updated: 2026-09-13 09:32

Details

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

SUNRPC: harden gss_unwrap_resp_priv length checks

gss_unwrap_resp_priv() validates the RPCSEC_GSS opaque length with

offset = (u8 *)(p) - (u8 *)head->iov_base;
if (offset + opaque_len > rcv_buf->len)
        goto unwrap_failed;
maj_stat = gss_unwrap(ctx->gc_gss_ctx, offset,
                      offset + opaque_len, rcv_buf);

Both operands are u32 and the sum is computed in u32. A reply with opaque_len near 0xffffffff makes offset + opaque_len wrap to a small value that is below rcv_buf->len, so the bound check passes and gss_unwrap() is called with end < begin. The check also lacks a lower bound, so any opaque_len in [0, GSS_KRB5_TOK_HDR_LEN) is accepted and forwarded to gss_krb5_unwrap_v2(), whose pre-decrypt header reads at ptr+4 and ptr+6 then run past the token.

A krb5p NFS server returning a crafted RPCSEC_GSS reply can drive the client into out-of-bounds reads in gss_krb5_unwrap_v2() and the rotate_left() loop that follows.

Fix by replacing the single combined check with three guards that are safe in u32 arithmetic and that enforce the RFC 4121 minimum outer token length:

if (offset > rcv_buf->len)
        goto unwrap_failed;
if (opaque_len > rcv_buf->len - offset)
        goto unwrap_failed;
if (opaque_len < GSS_KRB5_TOK_HDR_LEN)
        goto unwrap_failed;

The first guard makes the subtraction in the second guard unconditionally safe; offset is derived from a successful xdr_inline_decode() in the head kvec, so in practice it already satisfies the bound. The floor mirrors the server-side check added in commit 5b757c2e57a5 ("SUNRPC: svcauth_gss: enforce krb5 token minimum length").

Severity

9.8 (Critical)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-89541"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-11T20:19:37Z",
    "severity": "CRITICAL"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: harden gss_unwrap_resp_priv length checks\n\ngss_unwrap_resp_priv() validates the RPCSEC_GSS opaque length with\n\n    offset = (u8 *)(p) - (u8 *)head-\u003eiov_base;\n    if (offset + opaque_len \u003e rcv_buf-\u003elen)\n            goto unwrap_failed;\n    maj_stat = gss_unwrap(ctx-\u003egc_gss_ctx, offset,\n                          offset + opaque_len, rcv_buf);\n\nBoth operands are u32 and the sum is computed in u32. A reply with\nopaque_len near 0xffffffff makes offset + opaque_len wrap to a small\nvalue that is below rcv_buf-\u003elen, so the bound check passes and\ngss_unwrap() is called with end \u003c begin. The check also lacks a\nlower bound, so any opaque_len in [0, GSS_KRB5_TOK_HDR_LEN) is\naccepted and forwarded to gss_krb5_unwrap_v2(), whose pre-decrypt\nheader reads at ptr+4 and ptr+6 then run past the token.\n\nA krb5p NFS server returning a crafted RPCSEC_GSS reply can drive\nthe client into out-of-bounds reads in gss_krb5_unwrap_v2() and the\nrotate_left() loop that follows.\n\nFix by replacing the single combined check with three guards that\nare safe in u32 arithmetic and that enforce the RFC 4121 minimum\nouter token length:\n\n    if (offset \u003e rcv_buf-\u003elen)\n            goto unwrap_failed;\n    if (opaque_len \u003e rcv_buf-\u003elen - offset)\n            goto unwrap_failed;\n    if (opaque_len \u003c GSS_KRB5_TOK_HDR_LEN)\n            goto unwrap_failed;\n\nThe first guard makes the subtraction in the second guard\nunconditionally safe; offset is derived from a successful\nxdr_inline_decode() in the head kvec, so in practice it already\nsatisfies the bound. The floor mirrors the server-side check added\nin commit 5b757c2e57a5 (\"SUNRPC: svcauth_gss: enforce krb5 token\nminimum length\").",
  "id": "GHSA-8h82-j8r3-jr82",
  "modified": "2026-09-13T09:32:17Z",
  "published": "2026-09-11T21:31:31Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89541"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/87831b92112c81db251d46756d65daa4f91af6a2"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/89a15a50f84d32d4b99db86f957427fcbe20a99a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d395c30d570ca6168f0297b191709927d1258273"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ebcbd2523a8524c3d24e111cdbed8e271d910269"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

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.

Action not permitted

CVE-2026-89541 (GCVE-0-2026-89541)

FKIE_CVE-2026-89541

GHSA-8H82-J8R3-JR82

Tags

Sightings

Nomenclature