CVE-2026-89631

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 sizet.  The later subtraction wraps the _u16

bytesleft, and that is what bounds cifsstrndupfromutf16(): a bound of

up to 65535 against a ~16 KB cifsreqpoolp 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 smbeiotrace entry, which __mode(byte)

cannot represent, so the attribute goes with it.