CVE-2026-68431
CriticalCVSS 9.1Exploitation Probability (EPSS)
Low risk1th percentile - higher than 1% of all known CVEs
Summary
In the Linux kernel's ksmbd server, there is a missing validation of the minimum PDU size for transform requests. A packet with SMB2_TRANSFORM_PROTO_NUM bypasses the check, potentially leading to out-of-bounds read and disclosure of data to an unauthenticated client.
Risk Assessment
The vulnerability may allow an unauthenticated client to read kernel memory, potentially leading to disclosure of sensitive information or further attacks.
Recommendation
Apply the Linux kernel update containing the fix that validates the minimum PDU size for transform requests.
Original NVD description (English source)
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 SMB2_PROTO_NUMBER. A packet carrying SMB2_TRANSFORM_PROTO_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 init_smb2_rsp_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 SMB2_MIN_SUPPORTED_PDU_SIZE and require encryption transform requests to contain both a transform header and an SMB2 header. This rejects truncated requests before work allocation.