CVE-2026-68431

Critical

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.

Package Linux Kernel
Published 2026-08-12
Last modified 2026-08-23
CVSS version 3.1
Patch available
Yes

CVSS 3.1 score

9.1

out of 10
Critical
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
High
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Affected versions

Linux kernel versions 5.15.145, 6.1.34, 6.3.8, 6.4 and later are affected. Fixed in 5.15.217, 6.1.184, 6.6.153, 6.12.105, 6.18.46, 7.1.6, 7.2 and their respective stable series.

Affected from
≥ 5.15.145 ≥ 6.1.34 ≥ 6.3.8 ≥ 6.4
Fixed in
✓ 5.15.217 5.15.x ✓ 6.1.184 6.1.x ✓ 6.6.153 6.6.x ✓ 6.12.105 6.12.x ✓ 6.18.46 6.18.x ✓ 7.1.6 7.1.x ✓ 7.2

References

7 total
Showing 5 of 7 references View all on NVD

Frequently asked questions

  • What is CVE-2026-68431?

    CVE-2026-68431 is a Critical severity Linux kernel vulnerability with a CVSS score of 9.1 out of 10 . It affects Linux kernel versions from 5.15.145 onward and has been patched in 5.15.217, 6.1.184, 6.6.153 and others. CVE-2026-68431 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

  • What is the CVSS score for CVE-2026-68431?

    CVE-2026-68431 has a CVSS score of 9.1 out of 10, rated Critical severity (CVSS 3.1). The vector string is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H .

  • Is there a patch available for CVE-2026-68431?

    Yes. CVE-2026-68431 has been patched. Fixed versions include 5.15.217, 6.1.184, 6.6.153 and others. If you are running Linux kernel 5.15.145 or later up to the fix versions, apply the relevant patch for your kernel branch.

  • Is CVE-2026-68431 actively exploited?

    No. CVE-2026-68431 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

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