What is CVE-2026-74521?

CVE-2026-74521 is a Critical severity Linux kernel vulnerability with a CVSS score of 9.1 out of 10, affecting Linux kernel versions from 5.15 onward and patched in 6.1.189, 6.6.158, 6.12.111 and others. CVE-2026-74521 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

What is the CVSS score for CVE-2026-74521?

CVE-2026-74521 has a CVSS score of 9.1 out of 10, rated Critical severity. The vector string is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.

Is there a patch available for CVE-2026-74521?

Yes, CVE-2026-74521 has been patched. Fixed versions include 6.1.189, 6.6.158, 6.12.111 and others. If you are running Linux kernel 5.15 or later up to the fix versions, apply the relevant patch for your kernel branch.

Is CVE-2026-74521 actively exploited?

CVE-2026-74521 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

CVE-2026-74521

Critical

In the Linux kernel, the following vulnerability has been resolved: ksmbd: use memcmp() to compare ClientGUIDs ClientGUID is a fixed-size binary value and can contain embedded NUL bytes. strncmp() stops comparing at the first NUL byte, so different ClientGUID values can incorrectly be treated as equal. Use memcmp() in SMB3 multichannel session binding and FSCTL_VALIDATE_NEGOTIATE_INFO to compare all SMB2_CLIENT_GUID_SIZE bytes.

Package Linux Kernel

Published 2026-08-15

Last modified 2026-10-03

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

High

Availability

None

Vector string

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected versions

Linux kernel versions 5.15 and later are affected. Fixed in 6.1.189, 6.6.158, 6.12.111, 6.18.53, 7.1.8, 7.2 and their respective stable series.

Affected from

≥ 5.15

Fixed in

✓ 6.1.189 6.1.x ✓ 6.6.158 6.6.x ✓ 6.12.111 6.12.x ✓ 6.18.53 6.18.x ✓ 7.1.8 7.1.x ✓ 7.2

References

6 total

Showing 5 of 6 references View all on NVD

Details

CVE ID CVE-2026-74521

Severity Critical

CVSS score 9.1 / 10

CVSS version 3.1

Published 2026-08-15

Modified 2026-10-03

KEV No

Patch

Yes

Package linux

Frequently asked questions

What is CVE-2026-74521?

CVE-2026-74521 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 onward and has been patched in 6.1.189, 6.6.158, 6.12.111 and others. CVE-2026-74521 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
What is the CVSS score for CVE-2026-74521?

CVE-2026-74521 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:H/A:N.
Is there a patch available for CVE-2026-74521?

Yes. CVE-2026-74521 has been patched. Fixed versions include 6.1.189, 6.6.158, 6.12.111 and others. If you are running Linux kernel 5.15 or later up to the fix versions, apply the relevant patch for your kernel branch.
Is CVE-2026-74521 actively exploited?

No. CVE-2026-74521 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.