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CVE-2026-63940

CRITICALCVSS 9.3/10EPSS 0.18%

Last modified

CVE-2026-63940 is a critical-severity vulnerability rated 9.3/10 on the CVSS scale. 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.. EPSS estimates a 0.18% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1
9.3/10

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

EPSS Probability
0.18%

7.8th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
LinuxLinux>= 291bd20d5d88814a73d43b55b9428feab2f28094, < 3b6035bc6bff20e89752ce4358bc4c9a9d5883f2; >= 291bd20d5d88814a73d43b55b9428feab2f28094, < 2254972d4d69e279ba4e87bf0968eb08ad0d3c92; >= 291bd20d5d88814a73d43b55b9428feab2f28094, < c30cde934c7813b4e3069765dac64ce3d31e34f2; >= 291bd20d5d88814a73d43b55b9428feab2f28094, < 3988bd2723de407ae90fa7a6f6029b4e60238c58
LinuxLinux5.11

References

Timeline

Published
Last Modified
Status
Awaiting Analysis

Frequently Asked Questions

What is CVE-2026-63940?
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.
How severe is CVE-2026-63940?
CVE-2026-63940 has a CVSS score of 9.3/10 (CRITICAL severity). The EPSS model estimates a 0.18% probability of exploitation in the next 30 days.
How do I fix CVE-2026-63940?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST