CVE-2026-68431
Received Received - Intake

ksmbd Transform Request Handling Buffer Overflow

Publication date: 2026-08-12

Last updated on: 2026-08-12

Assigner: kernel.org

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.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published
2026-08-12
Last Modified
2026-08-12
Generated
2026-08-12
AI Q&A
2026-08-12
EPSS Evaluated
N/A
NVD
CVE-2026-68431
EUVD
EUVD-2026-57039

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
linux_kernel ksmbd *
linux linux_kernel to 2.1 (exc)

Helpful Resources

Exploitability

CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-UNKNOWN

Attack-Flow Graph

AI Quick Actions

Instant insights powered by AI
Executive Summary

This vulnerability in the Linux kernel's ksmbd component involves improper validation of SMB2 protocol data units (PDUs). When a packet uses SMB2_TRANSFORM_PROTO_NUM instead of SMB2_PROTO_NUMBER, the minimum size check is skipped. On SMB 2.1 connections, this allows a short transform packet to be misinterpreted as a full SMB2 header, leading to reading beyond allocated memory. The issue arises because compression transforms are converted to SMB2 messages before validation, bypassing proper checks.

Impact Analysis

This flaw could allow unauthenticated attackers to send malformed packets that cause memory corruption or crashes in the Linux kernel. Systems using ksmbd for SMB file sharing may experience denial-of-service conditions or potential remote code execution if exploited. Users relying on SMB 2.1 connections are particularly at risk.

Mitigation Strategies

Update the Linux kernel to the latest patched version to resolve the ksmbd vulnerability. Ensure SMB2 protocol validation is enforced and truncated requests are rejected before processing.

Chat Assistant

Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-68431. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70

EPSS Chart