CVE-2026-68431

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: validate minimum PDU size for transform requests

The receive path applies the minimum SMB2 PDU size check only when

ProtocolId is SMB2PROTONUMBER. A packet carrying

SMB2TRANSFORMPROTO_NUM bypasses the check even when the negotiated

dialect does not provide transform handling.

On an SMB 2.1 connection, a short transform packet therefore reaches

initsmb2rsp_hdr(), which interprets the request as a full SMB2 header

and reads beyond the request allocation. The copied fields can then be

returned to the unauthenticated client.

Compression transforms are converted to ordinary SMB2 messages before

protocol validation. After that conversion, validate ordinary SMB2

requests against SMB2MINSUPPORTEDPDUSIZE and require encryption

transform requests to contain both a transform header and an SMB2

header. This rejects truncated requests before work allocation.