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ksmbd: require 3 sub-authorities before reading sub_auth[2]

Type: advisorySource: Official CVE List1 source record

In the Linux kernel, the following vulnerability has been resolved: ksmbd: require 3 sub-authorities before reading sub_auth[2] parse_dacl() compares each ACE SID against sid_unix_NFS_mode and on match reads sid.sub_auth[2] as the file mode. If sid_unix_NFS_mode is the prefix S-1-5-88-3 with num_subauth = 2 then compare_sids() compares only min(num_subauth, 2) sub-authorities so a client SID with num_subauth = 2 and sub_auth = {88, 3} will match. If num_subauth = 2 and the ACE is placed at the very end of the security descriptor, sub_auth[2] will be 4 bytes past end_of_acl. The out-of-band bytes will then be masked to the low 9 bits and applied as the file's POSIX mode, probably not something that is good to have happen. Fix this up by forcing the SID to actually carry a third sub-authority before reading it at all.

Announced Source revision 1
Original source ↗

CVE-2026-31611

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-31611

Linux

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Linux

Source reference: /containers/cna/affected/1/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
        "lessThan": "cf2148b880fb7c0fcd727202dbc4fd5d6998b9c2",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
        "lessThan": "b5b5d5936a50497fb151c0b122899a6894721c2b",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
        "lessThan": "08f9e6d899b5c834bbcc239eae1bed58d9b15d2c",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
        "lessThan": "d2454f4a002d08560a60f214f392e6491cf11560",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
        "lessThan": "46bbcd3ebfb3549c8da1838fc4493e79bd3241e7",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
        "lessThan": "9401f86a224f37b50e6a3ccf1d46a70d5ef8af0a",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
        "lessThan": "53370cf9090777774e07fd9a8ebce67c6cc333ab",
        "versionType": "git"
      }
    ],
    "programFiles": [
      "fs/smb/server/smbacl.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "5.15"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "5.15",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "6.1.175",
        "versionType": "semver",
        "lessThanOrEqual": "6.1.*"
      },
      {
        "status": "unaffected",
        "version": "6.6.136",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.83",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.24",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "6.19.14",
        "versionType": "semver",
        "lessThanOrEqual": "6.19.*"
      },
      {
        "status": "unaffected",
        "version": "7.0.1",
        "versionType": "semver",
        "lessThanOrEqual": "7.0.*"
      },
      {
        "status": "unaffected",
        "version": "7.1",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "fs/smb/server/smbacl.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-31611

Source reference: /cveMetadata/cveId

Publisher severity

high

Source reference: /containers/cna/metrics

Event
#28298 · Revision 1
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Publisher date
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