CVE-2026-31709

Advisory lineage Upstream: 0 Downstream: 15
Modified
Published: 01 May 2026, 13:56
Last modified:15 Jul 2026, 01:08

Vulnerability Summary

Overall Risk (default)
medium
35/100
CVSS Score
8.8 HIGH
v3.1 (cve.org)
EPSS Score
0.26% LOW
0% probability 0.00%
KEV
Not listed
Ransomware
No reports
Public exploits
None found
Dark Web
Not detected

Timeline

01 May 2026, 13:56
Published
Vulnerability first disclosed
15 Jul 2026, 01:08
Last Modified
Vulnerability information updated

Description

In 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.

CVSS Metrics

  • v3.1•HIGH•Score: 8.8CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS Trends

Current EPSS score: 0.26%• Percentile: 17%

Techniques & Countermeasures

  • CWE-1288•Improper Validation of Consistency within Input

    The product receives a complex input with multiple elements or fields that must be consistent with each other, but it does not validate or incorrectly validates that the input is actually consistent.

Affected Systems

  • linux•linux

    ≥ bc3e9dd9d104ca1b75644eab87b38ce8a924aef4, < b8603d9ae6c9087662b098619996bc4a8064319d | ≥ bc3e9dd9d104ca1b75644eab87b38ce8a924aef4, < c2abdebf72000a64603ced84d36ccbd164f11391 | ≥ bc3e9dd9d104ca1b75644eab87b38ce8a924aef4, < 8e47d297e7cf9a6029a0d38e7b22faba7d7aaf12 | ≥ bc3e9dd9d104ca1b75644eab87b38ce8a924aef4, < d92f3f0b22414e7515696a02224d0af55e3004a3 | ≥ bc3e9dd9d104ca1b75644eab87b38ce8a924aef4, < ff0ca46b13b9ef6edbcd238a3b6caacfef8ba0e5 | ≥ bc3e9dd9d104ca1b75644eab87b38ce8a924aef4, < b78db9bddc84136f6a0bb49e8883cf200dfb87a8 | ≥ bc3e9dd9d104ca1b75644eab87b38ce8a924aef4, < 0a8cf165566ba55a39fd0f4de172119dd646d39a | 5.12

  • linux•linux kernel

    ≥ 5.12, < 7.0.2

References (19)