What’s Vulnerable › Vulnerabilities

CVE-2026-64380: smb: client: harden POSIX SID length parsing

• Severity: high (CVSS 8.2 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-25 · updated 2026-10-19
• Weakness: CWE-125

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 products

• Linux kernel: from 5.7 before 5.10.261; from 5.11 before 5.15.212; from 5.16 before 6.1.178; from 6.2 before 6.6.145; from 6.7 before 6.12.96; from 6.13 before 6.18.39 — fixed in 5.10.261, 5.15.212, 6.1.178, 6.12.96, 6.18.39, 6.6.145

How to fix

Upgrade to a fixed version: Linux kernel 5.10.261, 5.15.212, 6.1.178, 6.12.96. Check the vendor advisory for mitigations.

References

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

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