CVE-2026-64380: smb: client: harden POSIX SID length parsing
In the Linux kernel, the following vulnerability has been resolved:
smb: client: harden POSIX SID length parsing
posixinfosidsize() 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 Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 6.6.145.2-1 - Compensating control
For the SMB client hardening (POSIX SID length parsing), ensure the POSIX SID helper requires at least two bytes before reading sid[1] to get the subauthority count, and reject buffers that contain only one remaining byte (truncated POSIX SIDs).