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CVE-2026-64380

smb: client: harden POSIX SID length parsing

HIGH
8.2
CVSS Score
Published: July 25, 2026 at 08:50 AM UTC
Updated: October 19, 2026 at 09:17 PM UTC
1 product affected across 1 vendorLinux Kernel

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Severity
HIGH8.2
Exploit prediction
EPSS 0.4%
SSVC
No known exploit

Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: harden POSIX SID length parsing posix_info_sid_size() reads sid[1] to obtain the subauthority count, but its existing boundary check still accepts buffers with only one remaining byte. Require two bytes before reading sid[1] so all client paths that reuse the helper reject truncated POSIX SIDs safely.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Linux Kernel· Linux
95%
5.11 ≤ v < 5.15.2125.16 ≤ v < 6.1.1785.7 ≤ v < 5.10.2616.13 ≤ v < 6.18.396.19 ≤ v < 7.1.46.2 ≤ v < 6.6.1456.7 ≤ v < 6.12.96349e13ad30b45998bb9937cfe0b32be6f951976d7.27.2 rc1
Vendor states this is fixed in 0de5b8e76847f5de26f364a82c6602c4881c30da (fixed)
Vendor states this is fixed in 171605aed68380c2fa75dff9b3a1ed427c50065b (fixed)
Vendor states this is fixed in 4213c1208978483021d7d125c131de3985d38f61 (fixed)
Vendor states this is fixed in 427eb7eb46425fec845a43e861f3d6e2899cae59 (fixed)
Vendor states this is fixed in 46a84715a015cb48e1b9c219dc88c03d8a541ea4 (fixed)
Vendor states this is fixed in 7ad2bcf2441430bb2e918fb3ef9a90d775a6e422 (fixed)
Vendor states this is fixed in 86c5d470f5d42e61123b2f4b4f0b91f4eee5b980 (fixed)
Vendor states this is fixed in 96e889bc1e759c83f25093e8c2f3da31b4973f30 (fixed)
Vendor states this is fixed in 5.10.261 (unaffected)
Vendor states this is fixed in 5.15.212 (unaffected)
Vendor states this is fixed in 5.7 (unaffected)
Vendor states this is fixed in 6.1.178 (unaffected)
Vendor states this is fixed in 6.12.96 (unaffected)
Vendor states this is fixed in 6.18.39 (unaffected)
Vendor states this is fixed in 6.6.145 (unaffected)
Vendor states this is fixed in 7.1.4 (unaffected)
Vendor states this is fixed in 7.2 (unaffected)

References (8)

Patch
Source: cverecord
https://git.kernel.org/stable/c/171605aed68380c2fa75dff9b3a1ed427c50065b
Patch
Source: cverecord
https://git.kernel.org/stable/c/4213c1208978483021d7d125c131de3985d38f61
Patch
Source: cverecord
https://git.kernel.org/stable/c/96e889bc1e759c83f25093e8c2f3da31b4973f30
Patch
Source: cverecord
https://git.kernel.org/stable/c/0de5b8e76847f5de26f364a82c6602c4881c30da
Patch
Source: cverecord
https://git.kernel.org/stable/c/427eb7eb46425fec845a43e861f3d6e2899cae59
Patch
Source: cverecord
https://git.kernel.org/stable/c/86c5d470f5d42e61123b2f4b4f0b91f4eee5b980
Patch
Source: cverecord
https://git.kernel.org/stable/c/46a84715a015cb48e1b9c219dc88c03d8a541ea4
Patch
Source: cverecord
https://git.kernel.org/stable/c/7ad2bcf2441430bb2e918fb3ef9a90d775a6e422

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

8.2HIGHLinux
Vector?

Quick Info

StatusMODIFIED
CWE
NVD-CWE-noinfoCWE-125

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