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

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Summary

CVECVE-2026-89631
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-11 20:19:48 UTC
Updated2026-09-11 20:19:48 UTC
DescriptionIn 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.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected cc20c031bb067eb3280a1c4b5c42295093e24863 3be89e8039a85fa3b6cd5f9dcc4c1459eb356c2d git Not specified
CNA Linux Linux affected cc20c031bb067eb3280a1c4b5c42295093e24863 411e484fe71a7f1028de617447edad9cb6d9d68a git Not specified
CNA Linux Linux affected cc20c031bb067eb3280a1c4b5c42295093e24863 65deb18359341141d37dc86fc7853511be3c87a7 git Not specified
CNA Linux Linux affected 2.6.30 Not specified
CNA Linux Linux unaffected 2.6.30 semver Not specified
CNA Linux Linux unaffected 6.18.51 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.4 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/65deb18359341141d37dc86fc7853511be3c87a7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/411e484fe71a7f1028de617447edad9cb6d9d68a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/3be89e8039a85fa3b6cd5f9dcc4c1459eb356c2d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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