CVE-2026-89631: smb: client: reject a tree connect response whose byte count is too small

Description

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.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

cc20c031bb067eb3280a1c4b5c42295093e24863 to < d837645a719151ed392d4d9cab4571c2753dab12affected
cc20c031bb067eb3280a1c4b5c42295093e24863 to < 2ae219762ebac929bf6ab3473681f10ed566af08affected
cc20c031bb067eb3280a1c4b5c42295093e24863 to < 3be89e8039a85fa3b6cd5f9dcc4c1459eb356c2daffected
cc20c031bb067eb3280a1c4b5c42295093e24863 to < 411e484fe71a7f1028de617447edad9cb6d9d68aaffected
cc20c031bb067eb3280a1c4b5c42295093e24863 to < 65deb18359341141d37dc86fc7853511be3c87a7affected

Linux Linux

Default version status: affected

2.6.30affected
0 to < 2.6.30unaffected
6.6.160 to ≤ 6.6.*unaffected
6.12.114 to ≤ 6.12.*unaffected
6.18.51 to ≤ 6.18.*unaffected
7.2.4 to ≤ 7.2.*unaffected
7.3 to ≤ *unaffected

CVE-2026-89631

smb: client: reject a tree connect response whose byte count is too small

Description

Affected products

Linux Linux

Linux Linux

References