CVE-2026-68431

/// Technical description

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.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References