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.

A flaw was found in the Linux kernel's Server Message Block (SMB) client. The vulnerability exists in the `posix_info_sid_size()` function, which is responsible for parsing POSIX Security Identifiers (SIDs). An insufficient boundary check allows the system to accept truncated POSIX SIDs, which could lead to unexpected behavior or a denial of service. This issue has been resolved by requiring at least two bytes before reading the subauthority count, ensuring that all client paths safely reject malformed SIDs.

Red Hat Enterprise Linux 10 Affected kernel Red Hat Enterprise Linux 6 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel-rt Red Hat Enterprise Linux 8 Affected kernel Red Hat Enterprise Linux 8 Affected kernel-rt Red Hat Enterprise Linux 9 Affected kernel Red Hat Enterprise Linux 9 Affected kernel-rt https://www.cve.org/CVERecord?id=CVE-2026-64380 https://nvd.nist.gov/vuln/detail/CVE-2026-64380 https://lore.kernel.org/linux-cve-announce/2026072525-CVE-2026-64380-95d8@gregkh/T