CVE-2026-64380 (CVSS 8.2)

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.

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CVSS v3.1 Score

8.2

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H

EPSS — Exploit Prediction

0.0044

Probability of exploitation

0.36%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

References

Other 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

Frequently Asked Questions

What is CVE-2026-64380? +

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. It has a CVSS v3.1 base score of 8.2 (HIGH).

How severe is CVE-2026-64380? +

CVE-2026-64380 has a CVSS v3.1 score of 8.2 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0044, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-64380? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

CVE-2026-64380