What is CVE-2026-63940?

CVE-2026-63940 is a Critical severity Linux kernel vulnerability with a CVSS score of 9.3 out of 10, affecting Linux kernel versions from 5.11 onward and patched in 6.12.95, 6.18.35, 7.0.12 and others. CVE-2026-63940 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

What is the CVSS score for CVE-2026-63940?

CVE-2026-63940 has a CVSS score of 9.3 out of 10, rated Critical severity. The vector string is CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H.

Is there a patch available for CVE-2026-63940?

Yes, CVE-2026-63940 has been patched. Fixed versions include 6.12.95, 6.18.35, 7.0.12 and others. If you are running Linux kernel 5.11 or later up to the fix versions, apply the relevant patch for your kernel branch.

Is CVE-2026-63940 actively exploited?

CVE-2026-63940 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

CVE-2026-63940

Critical

In the Linux kernel, the following vulnerability has been resolved: KVM: SEV: Ignore Port I/O requests of length '0' Explicitly ignore Port I/O requests of length '0' (or count '0'), so that setting up the software scratch area (and other code) doesn't have to worry about underflowing the length, and to allow for WARNing on trying to configure the scratch area with len==0.

Package Linux Kernel

Published 2026-07-19

Last modified 2026-07-27

CVSS version 3.1

Patch available

Yes

CVSS 3.1 score

9.3

out of 10

Critical

Attack Vector

Local

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Changed

Confidentiality

High

Integrity

High

Availability

High

Vector string

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

Affected versions

Linux kernel versions 5.11 and later are affected. Fixed in 6.12.95, 6.18.35, 7.0.12, 7.1 and their respective stable series.

Affected from

≥ 5.11

Fixed in

✓ 6.12.95 6.12.x ✓ 6.18.35 6.18.x ✓ 7.0.12 7.0.x ✓ 7.1

References

4 total

Details

CVE ID CVE-2026-63940

Severity Critical

CVSS score 9.3 / 10

CVSS version 3.1

Published 2026-07-19

Modified 2026-07-27

KEV No

Patch

Yes

Package linux

Frequently asked questions

What is CVE-2026-63940?

CVE-2026-63940 is a Critical severity Linux kernel vulnerability with a CVSS score of 9.3 out of 10 . It affects Linux kernel versions from 5.11 onward and has been patched in 6.12.95, 6.18.35, 7.0.12 and others. CVE-2026-63940 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
What is the CVSS score for CVE-2026-63940?

CVE-2026-63940 has a CVSS score of 9.3 out of 10, rated Critical severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H.
Is there a patch available for CVE-2026-63940?

Yes. CVE-2026-63940 has been patched. Fixed versions include 6.12.95, 6.18.35, 7.0.12 and others. If you are running Linux kernel 5.11 or later up to the fix versions, apply the relevant patch for your kernel branch.
Is CVE-2026-63940 actively exploited?

No. CVE-2026-63940 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.