CVE-2026-31709

High

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.

Package Linux Kernel
Published 2026-05-01
Last modified 2026-07-15
CVSS version 3.1
Patch available
Yes

CVSS 3.1 score

8.8

out of 10
High
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Weakness type

CWE-1288

CVE-2026-31709 is classified as CWE-1288

See CWE-1288 on MITRE CWE for full details on this weakness type.

Affected versions

Linux kernel versions 5.12 and later are affected. Fixed in 5.15.210, 6.1.176, 6.6.140, 6.12.86, 6.18.35, 7.0.2, 7.1 and their respective stable series.

Affected from
≥ 5.12
Fixed in
✓ 5.15.210 5.15.x ✓ 6.1.176 6.1.x ✓ 6.6.140 6.6.x ✓ 6.12.86 6.12.x ✓ 6.18.35 6.18.x ✓ 7.0.2 7.0.x ✓ 7.1

References

19 total
Showing 5 of 19 references View all on NVD

Frequently asked questions

  • What is CVE-2026-31709?

    CVE-2026-31709 is a High severity Linux kernel vulnerability with a CVSS score of 8.8 out of 10 . It affects Linux kernel versions from 5.12 onward and has been patched in 5.15.210, 6.1.176, 6.6.140 and others. CVE-2026-31709 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

  • What is the CVSS score for CVE-2026-31709?

    CVE-2026-31709 has a CVSS score of 8.8 out of 10, rated High severity (CVSS 3.1). The vector string is CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H .

  • Is there a patch available for CVE-2026-31709?

    Yes. CVE-2026-31709 has been patched. Fixed versions include 5.15.210, 6.1.176, 6.6.140 and others. If you are running Linux kernel 5.12 or later up to the fix versions, apply the relevant patch for your kernel branch.

  • Is CVE-2026-31709 actively exploited?

    No. CVE-2026-31709 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

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