DEBIAN-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 SMB2TRANSFORMPROTONUM 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 initsmb2rsphdr(), 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.