CVE-2026-68100 (GCVE-0-2026-68100)

Vulnerability from cvelistv5 – Published: 2026-08-10 11:58 – Updated: 2026-08-17 04:58
VLAI
Title
ksmbd: validate num_subauth when copying ACE in set_ntacl_dacl
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: validate num_subauth when copying ACE in set_ntacl_dacl set_ntacl_dacl() copies each ACE from the attacker-controlled stored security descriptor verbatim into the response DACL without checking sid.num_subauth. The ACE bytes (including an unchecked num_subauth) originate from an authenticated SMB2_SET_INFO(SecInfo=DACL) that is stored raw via ksmbd_vfs_set_sd_xattr(); parse_dacl() rejects a bad ACE with `break` rather than an error, so parse_sec_desc() still returns success and the malformed SD reaches the xattr intact. On a subsequent SMB2_QUERY_INFO(SecInfo=DACL) for an inode carrying a POSIX access ACL, build_sec_desc() -> set_ntacl_dacl() -> set_posix_acl_entries_dacl() walks the copied ACEs and reads ntace->sid.sub_auth[ntace->sid.num_subauth - 1] with num_subauth taken straight from the stored SD. Since sub_auth[] is fixed at SID_MAX_SUB_AUTHORITIES (15), a crafted num_subauth (e.g. 255) drives an out-of-bounds heap read of ~1 KB with an offset fully controlled by an authenticated client. The sibling functions already gate this field: parse_dacl() -- num_subauth == 0 || > SID_MAX_SUB_AUTHORITIES parse_sid() -- num_subauth > SID_MAX_SUB_AUTHORITIES smb_copy_sid() -- min_t(u8, num_subauth, SID_MAX_SUB_AUTHORITIES) set_ntacl_dacl() is the lone inconsistent path that omits the check. Add the same num_subauth validation in set_ntacl_dacl() before copying the ACE, matching the gate already enforced by parse_dacl().
Severity
8.1 (High)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < e31fada5143784bc05c7ae44c79eed9b7a2e147e (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < fb3dc8e6da46a1ccad1956cda57de29d9b3033e0 (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < b6d3cc6a524416dfdb2b47e4bba2e7e20011d056 (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 5acbd3012fd4a7ccfebd91ea6f784120084eb897 (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 47f0b34f6bc98ed85bfdc293e8f3e432ec24958d (git)
guessed Create a notification for this product.
Linux Linux Affected: 5.15
Unaffected: 0 , < 5.15 (semver)
Unaffected: 6.6.148 , ≤ 6.6.* (semver)
Unaffected: 6.12.101 , ≤ 6.12.* (semver)
Unaffected: 6.18.42 , ≤ 6.18.* (semver)
Unaffected: 7.1.6 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Show details on NVD website
To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/smbacl.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "e31fada5143784bc05c7ae44c79eed9b7a2e147e",
              "status": "affected",
              "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
              "versionType": "git"
            },
            {
              "lessThan": "fb3dc8e6da46a1ccad1956cda57de29d9b3033e0",
              "status": "affected",
              "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
              "versionType": "git"
            },
            {
              "lessThan": "b6d3cc6a524416dfdb2b47e4bba2e7e20011d056",
              "status": "affected",
              "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
              "versionType": "git"
            },
            {
              "lessThan": "5acbd3012fd4a7ccfebd91ea6f784120084eb897",
              "status": "affected",
              "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
              "versionType": "git"
            },
            {
              "lessThan": "47f0b34f6bc98ed85bfdc293e8f3e432ec24958d",
              "status": "affected",
              "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/smbacl.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.15"
            },
            {
              "lessThan": "5.15",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.148",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.101",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.42",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.148",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.101",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.42",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1.6",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: validate num_subauth when copying ACE in set_ntacl_dacl\n\nset_ntacl_dacl() copies each ACE from the attacker-controlled stored\nsecurity descriptor verbatim into the response DACL without checking\nsid.num_subauth. The ACE bytes (including an unchecked num_subauth)\noriginate from an authenticated SMB2_SET_INFO(SecInfo=DACL) that is\nstored raw via ksmbd_vfs_set_sd_xattr(); parse_dacl() rejects a bad ACE\nwith `break` rather than an error, so parse_sec_desc() still returns\nsuccess and the malformed SD reaches the xattr intact.\n\nOn a subsequent SMB2_QUERY_INFO(SecInfo=DACL) for an inode carrying a\nPOSIX access ACL, build_sec_desc() -\u003e set_ntacl_dacl() -\u003e\nset_posix_acl_entries_dacl() walks the copied ACEs and reads\n\n    ntace-\u003esid.sub_auth[ntace-\u003esid.num_subauth - 1]\n\nwith num_subauth taken straight from the stored SD. Since sub_auth[]\nis fixed at SID_MAX_SUB_AUTHORITIES (15), a crafted num_subauth (e.g.\n255) drives an out-of-bounds heap read of ~1 KB with an offset fully\ncontrolled by an authenticated client.\n\nThe sibling functions already gate this field:\n  parse_dacl()    -- num_subauth == 0 || \u003e SID_MAX_SUB_AUTHORITIES\n  parse_sid()     -- num_subauth \u003e SID_MAX_SUB_AUTHORITIES\n  smb_copy_sid()  -- min_t(u8, num_subauth, SID_MAX_SUB_AUTHORITIES)\nset_ntacl_dacl() is the lone inconsistent path that omits the check.\n\nAdd the same num_subauth validation in set_ntacl_dacl() before copying\nthe ACE, matching the gate already enforced by parse_dacl()."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.1,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - ksmbd is the in-kernel SMB3 server on TCP/445; both SMB2_SET_INFO(SecInfo=DACL) and SMB2_QUERY_INFO(SecInfo=DACL) are handled from remote SMB2 PDUs in smb2_set_info()/smb2_query_info() via ksmbd_conn_handler_loop(), with no local syscall or physical access required.\nAC:L - Once ksmbd is running with ACL-xattr shares, an attacker deterministically plants a malformed DACL via SET_INFO and triggers the read on QUERY_INFO; num_subauth fully controls the OOB offset, with no race, timing window, or victim-dependent memory layout required.\nPR:L - SMB2_SET_INFO/QUERY_INFO require a valid post-authentication session (smb2_check_user_session) and SET_INFO SECURITY additionally requires FILE_WRITE_DAC/FILE_WRITE_OWNER on the open handle; this is a low-privilege authenticated SMB client, not a pre-auth or root-only path.\nUI:N - Exploitation is driven entirely by the attacker\u0027s own SMB2 SET_INFO and QUERY_INFO requests over the network; no local user, administrator, or victim client must perform any separate action.\nS:U - The out-of-bounds read and any resulting disclosure or crash occur entirely within kernel ksmbd server memory on the host; no VM, IOMMU, container, or other security-boundary escape is involved.\nC:H - Crafted num_subauth (e.g. 255) makes set_posix_acl_entries_dacl() index far past the 15-element sub_auth[] array, performing an attacker-offset-controlled ~1 KB out-of-bounds kernel heap read whose value is compared during DACL rebuild, enabling kernel memory disclosure.\nI:N - The defect is an out-of-bounds read during ACE deduplication; no kernel memory is written, no attacker-controlled data is persisted beyond the intentionally stored security descriptor, and no code-execution or arbitrary-write primitive is introduced.\nA:H - An unchecked multi-hundred-byte read past the smb_ace SID sub_auth array can cross slab/object boundaries and fault on hardened or KASAN builds; any unvalidated kernel out-of-bounds access is treated as capable of oops/panic and full host denial of service."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T04:58:49.241Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/e31fada5143784bc05c7ae44c79eed9b7a2e147e"
        },
        {
          "url": "https://git.kernel.org/stable/c/fb3dc8e6da46a1ccad1956cda57de29d9b3033e0"
        },
        {
          "url": "https://git.kernel.org/stable/c/b6d3cc6a524416dfdb2b47e4bba2e7e20011d056"
        },
        {
          "url": "https://git.kernel.org/stable/c/5acbd3012fd4a7ccfebd91ea6f784120084eb897"
        },
        {
          "url": "https://git.kernel.org/stable/c/47f0b34f6bc98ed85bfdc293e8f3e432ec24958d"
        }
      ],
      "title": "ksmbd: validate num_subauth when copying ACE in set_ntacl_dacl",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-68100",
    "datePublished": "2026-08-10T11:58:15.233Z",
    "dateReserved": "2026-07-30T09:28:09.368Z",
    "dateUpdated": "2026-08-17T04:58:49.241Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-68100",
      "date": "2026-08-20",
      "epss": "0.00403",
      "percentile": "0.33799"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-68100\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-08-10T13:19:54.533\",\"lastModified\":\"2026-08-17T05:18:09.407\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nksmbd: validate num_subauth when copying ACE in set_ntacl_dacl\\n\\nset_ntacl_dacl() copies each ACE from the attacker-controlled stored\\nsecurity descriptor verbatim into the response DACL without checking\\nsid.num_subauth. The ACE bytes (including an unchecked num_subauth)\\noriginate from an authenticated SMB2_SET_INFO(SecInfo=DACL) that is\\nstored raw via ksmbd_vfs_set_sd_xattr(); parse_dacl() rejects a bad ACE\\nwith `break` rather than an error, so parse_sec_desc() still returns\\nsuccess and the malformed SD reaches the xattr intact.\\n\\nOn a subsequent SMB2_QUERY_INFO(SecInfo=DACL) for an inode carrying a\\nPOSIX access ACL, build_sec_desc() -\u003e set_ntacl_dacl() -\u003e\\nset_posix_acl_entries_dacl() walks the copied ACEs and reads\\n\\n    ntace-\u003esid.sub_auth[ntace-\u003esid.num_subauth - 1]\\n\\nwith num_subauth taken straight from the stored SD. Since sub_auth[]\\nis fixed at SID_MAX_SUB_AUTHORITIES (15), a crafted num_subauth (e.g.\\n255) drives an out-of-bounds heap read of ~1 KB with an offset fully\\ncontrolled by an authenticated client.\\n\\nThe sibling functions already gate this field:\\n  parse_dacl()    -- num_subauth == 0 || \u003e SID_MAX_SUB_AUTHORITIES\\n  parse_sid()     -- num_subauth \u003e SID_MAX_SUB_AUTHORITIES\\n  smb_copy_sid()  -- min_t(u8, num_subauth, SID_MAX_SUB_AUTHORITIES)\\nset_ntacl_dacl() is the lone inconsistent path that omits the check.\\n\\nAdd the same num_subauth validation in set_ntacl_dacl() before copying\\nthe ACE, matching the gate already enforced by parse_dacl().\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/smb/server/smbacl.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9\",\"lessThan\":\"e31fada5143784bc05c7ae44c79eed9b7a2e147e\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9\",\"lessThan\":\"fb3dc8e6da46a1ccad1956cda57de29d9b3033e0\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9\",\"lessThan\":\"b6d3cc6a524416dfdb2b47e4bba2e7e20011d056\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9\",\"lessThan\":\"5acbd3012fd4a7ccfebd91ea6f784120084eb897\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9\",\"lessThan\":\"47f0b34f6bc98ed85bfdc293e8f3e432ec24958d\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/smb/server/smbacl.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"5.15\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"5.15\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.6.148\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.101\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.42\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1.6\",\"lessThanOrEqual\":\"7.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2\",\"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:L/UI:N/S:U/C:H/I:N/A:H\",\"baseScore\":8.1,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":2.8,\"impactScore\":5.2}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/47f0b34f6bc98ed85bfdc293e8f3e432ec24958d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/5acbd3012fd4a7ccfebd91ea6f784120084eb897\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/b6d3cc6a524416dfdb2b47e4bba2e7e20011d056\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/e31fada5143784bc05c7ae44c79eed9b7a2e147e\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/fb3dc8e6da46a1ccad1956cda57de29d9b3033e0\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-13T23:19:23+00:00",
      "cve": "CVE-2026-68100",
      "id": "CVE-2026-68100",
      "initial_release_date": "2026-08-10T00:00:00+00:00",
      "product_status:known_affected": "262",
      "product_status:known_not_affected": "14",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: ksmbd: validate num_subauth when copying ACE in set_ntacl_dacl",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-68100.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-08-12T16:23:04Z",
      "cve": "CVE-2026-68100",
      "id": "CVE-2026-68100",
      "initial_release_date": "2026-08-12T16:23:04Z",
      "product_status:known_affected": "129",
      "product_status:known_not_affected": "167",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-68100",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-68100.json",
      "version": "2"
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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.