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In the Linux kernel, the following vulnerability has been resolved: smb: client: reject a tree connect response whose byte count is too small CIFSTCon() bounds its strnlen() over the byte area with the server's ByteCount minus two, which for ByteCount 0 or 1 goes negative as an int and converts to a huge size_t. The later subtraction wraps the __u16 bytes_left, and that is what bounds cifs_strndup_from_utf16(): a bound of up to 65535 against a ~16 KB cifs_req_poolp object runs off the end of the slab object, and the bytes reach userspace through tcon->nativeFileSystem in /proc/fs/cifs/DebugData. Reject a byte area too small for what the parser consumes. Two bytes is the least it can consume, and no conformant response carries fewer. The new trace point is the 129th smb_eio_trace entry, which __mode(byte) cannot represent, so the attribute goes with it.
Upstream advisory: https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89631.mbox
This issue has been addressed in the following products: Red Hat Enterprise Linux 10 Via RHSA-2026:85321 https://access.redhat.com/errata/RHSA-2026:85321
This issue has been addressed in the following products: Red Hat Enterprise Linux 8 Via RHSA-2026:85774 https://access.redhat.com/errata/RHSA-2026:85774
This issue has been addressed in the following products: Red Hat Enterprise Linux 8 Via RHSA-2026:85773 https://access.redhat.com/errata/RHSA-2026:85773