GHSA-8HP2-QMC6-F97H
Vulnerability from github – Published: 2026-05-01 15:30 – Updated: 2026-06-30 03:36In the Linux kernel, the following vulnerability has been resolved:
smb: client: validate the whole DACL before rewriting it in cifsacl
build_sec_desc() and id_mode_to_cifs_acl() derive a DACL pointer from a server-supplied dacloffset and then use the incoming ACL to rebuild the chmod/chown security descriptor.
The original fix only checked that the struct smb_acl header fits before reading dacl_ptr->size or dacl_ptr->num_aces. That avoids the immediate header-field OOB read, but the rewrite helpers still walk ACEs based on pdacl->num_aces with no structural validation of the incoming DACL body.
A malicious server can return a truncated DACL that still contains a header, claims one or more ACEs, and then drive replace_sids_and_copy_aces() or set_chmod_dacl() past the validated extent while they compare or copy attacker-controlled ACEs.
Factor the DACL structural checks into validate_dacl(), extend them to validate each ACE against the DACL bounds, and use the shared validator before the chmod/chown rebuild paths. parse_dacl() reuses the same validator so the read-side parser and write-side rewrite paths agree on what constitutes a well-formed incoming DACL.
{
"affected": [],
"aliases": [
"CVE-2026-31709"
],
"database_specific": {
"cwe_ids": [
"CWE-1288"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-05-01T14:16:20Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: validate the whole DACL before rewriting it in cifsacl\n\nbuild_sec_desc() and id_mode_to_cifs_acl() derive a DACL pointer from a\nserver-supplied dacloffset and then use the incoming ACL to rebuild the\nchmod/chown security descriptor.\n\nThe original fix only checked that the struct smb_acl header fits before\nreading dacl_ptr-\u003esize or dacl_ptr-\u003enum_aces. That avoids the immediate\nheader-field OOB read, but the rewrite helpers still walk ACEs based on\npdacl-\u003enum_aces with no structural validation of the incoming DACL body.\n\nA malicious server can return a truncated DACL that still contains a\nheader, claims one or more ACEs, and then drive\nreplace_sids_and_copy_aces() or set_chmod_dacl() past the validated\nextent while they compare or copy attacker-controlled ACEs.\n\nFactor the DACL structural checks into validate_dacl(), extend them to\nvalidate each ACE against the DACL bounds, and use the shared validator\nbefore the chmod/chown rebuild paths. parse_dacl() reuses the same\nvalidator so the read-side parser and write-side rewrite paths agree on\nwhat constitutes a well-formed incoming DACL.",
"id": "GHSA-8hp2-qmc6-f97h",
"modified": "2026-06-30T03:36:28Z",
"published": "2026-05-01T15:30:33Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31709"
},
{
"type": "WEB",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31709.json"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ff0ca46b13b9ef6edbcd238a3b6caacfef8ba0e5"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d92f3f0b22414e7515696a02224d0af55e3004a3"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c2abdebf72000a64603ced84d36ccbd164f11391"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b8603d9ae6c9087662b098619996bc4a8064319d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b78db9bddc84136f6a0bb49e8883cf200dfb87a8"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8e47d297e7cf9a6029a0d38e7b22faba7d7aaf12"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0a8cf165566ba55a39fd0f4de172119dd646d39a"
},
{
"type": "WEB",
"url": "https://bugzilla.redhat.com/show_bug.cgi?id=2464476"
},
{
"type": "WEB",
"url": "https://access.redhat.com/security/cve/CVE-2026-31709"
},
{
"type": "WEB",
"url": "https://access.redhat.com/errata/RHSA-2026:24343"
},
{
"type": "WEB",
"url": "https://access.redhat.com/errata/RHSA-2026:23329"
},
{
"type": "WEB",
"url": "https://access.redhat.com/errata/RHSA-2026:23237"
},
{
"type": "WEB",
"url": "https://access.redhat.com/errata/RHSA-2026:23224"
},
{
"type": "WEB",
"url": "https://access.redhat.com/errata/RHSA-2026:22940"
},
{
"type": "WEB",
"url": "https://access.redhat.com/errata/RHSA-2026:22900"
},
{
"type": "WEB",
"url": "https://access.redhat.com/errata/RHSA-2026:21745"
},
{
"type": "WEB",
"url": "https://access.redhat.com/errata/RHSA-2026:21706"
},
{
"type": "WEB",
"url": "https://access.redhat.com/errata/RHSA-2026:21556"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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