CVE-2026-31611 (GCVE-0-2026-31611)
Vulnerability from cvelistv5
Published
2026-04-24 14:42
Modified
2026-04-27 14:04
Severity ?
VLAI Severity ?
EPSS score ?
Summary
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.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 Version: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 Version: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 Version: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 Version: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 Version: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 |
||
{
"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": [
{
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},
{
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},
{
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"status": "affected",
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"versionType": "git"
},
{
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"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": "6.6.136",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.83",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.24",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.19.*",
"status": "unaffected",
"version": "6.19.14",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.0.*",
"status": "unaffected",
"version": "7.0.1",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.1-rc1",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.136",
"versionStartIncluding": "5.15",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.83",
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"vulnerable": true
},
{
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"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.19.14",
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"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "5.15",
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},
{
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"versionEndExcluding": "7.1-rc1",
"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: require 3 sub-authorities before reading sub_auth[2]\n\nparse_dacl() compares each ACE SID against sid_unix_NFS_mode and on\nmatch reads sid.sub_auth[2] as the file mode. If sid_unix_NFS_mode is\nthe prefix S-1-5-88-3 with num_subauth = 2 then compare_sids() compares\nonly min(num_subauth, 2) sub-authorities so a client SID with\nnum_subauth = 2 and sub_auth = {88, 3} will match.\n\nIf num_subauth = 2 and the ACE is placed at the very end of the security\ndescriptor, sub_auth[2] will be 4 bytes past end_of_acl. The\nout-of-band bytes will then be masked to the low 9 bits and applied as\nthe file\u0027s POSIX mode, probably not something that is good to have\nhappen.\n\nFix this up by forcing the SID to actually carry a third sub-authority\nbefore reading it at all."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 8.6,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H",
"version": "3.1"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-04-27T14:04:23.206Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/b5b5d5936a50497fb151c0b122899a6894721c2b"
},
{
"url": "https://git.kernel.org/stable/c/08f9e6d899b5c834bbcc239eae1bed58d9b15d2c"
},
{
"url": "https://git.kernel.org/stable/c/d2454f4a002d08560a60f214f392e6491cf11560"
},
{
"url": "https://git.kernel.org/stable/c/46bbcd3ebfb3549c8da1838fc4493e79bd3241e7"
},
{
"url": "https://git.kernel.org/stable/c/9401f86a224f37b50e6a3ccf1d46a70d5ef8af0a"
},
{
"url": "https://git.kernel.org/stable/c/53370cf9090777774e07fd9a8ebce67c6cc333ab"
}
],
"title": "ksmbd: require 3 sub-authorities before reading sub_auth[2]",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-31611",
"datePublished": "2026-04-24T14:42:32.124Z",
"dateReserved": "2026-03-09T15:48:24.122Z",
"dateUpdated": "2026-04-27T14:04:23.206Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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