smb: client: harden POSIX SID length parsing
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.
02 / AFFECTED SOFTWARE
Affected packages
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
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.
05 / REFERENCES
Further evidence
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
- 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
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64380.json
- https://nvd.nist.gov/vuln/detail/CVE-2026-64380