CVE-2026-31709

Advisory lineage Upstream: 0 Downstream: 8
Modified
Published: 01 May 2026, 13:56
Last modified:17 May 2026, 15:21

Vulnerability Summary

Overall Risk (default)
medium
35/100
CVSS Score
8.8 HIGH
v3.1 (cve.org)
EPSS Score
0.05% 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
17 May 2026, 15:21
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: 0.05%• Percentile: 17%

Affected Systems

  • linux•linux

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

  • linux•linux_kernel

    ≥ 5.12, < 7.0.2

References (4)