CVE-2026-63939
9.3 · CRITICALOverview
CVE-2026-63939 is a critical-severity vulnerability. It was published on July 19, 2026 and has a CVSS 3.1 base score of 9.3 (CRITICAL).
This vulnerability has a CVSS 3.1 base score of 9.3, rated CRITICAL. It requires local or adjacent network access to exploit. No authentication or special privileges are required for exploitation.
Technical Description
In the Linux kernel, the following vulnerability has been resolved:
KVM: SEV: Compute the correct max length of the in-GHCB scratch area
When setting the length of the GHCB scratch area, and the area is in the
GHCB shared buffer, set the effective length of the scratch area to the max
possible size given the start of the guest-provided pointer, and the end of
the shared buffer.
The code was "fine" when first introduced, as KVM doesn't consult the
length of the buffer when emulating MMIO, because the passed in @len always
specifies the *max* size required. But for PSC requests, the incoming @len
is just the minimum length (to process the header), and KVM needs to know
the full size of the scratch area to avoid buffer overflows (spoiler alert).
Opportunistically rename @len => @min_len to better reflect its role.
Remediation
Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Frequently Asked Questions
What is CVE-2026-63939?
CVE-2026-63939 is a critical-severity vulnerability. It was published on July 19, 2026 and has a CVSS 3.1 base score of 9.3 (CRITICAL).
How severe is CVE-2026-63939?
This vulnerability has a CVSS 3.1 base score of 9.3, rated CRITICAL. It requires local or adjacent network access to exploit. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2026-63939?
Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-63939?
CyberStrike's AI-powered security agents can automatically detect CVE-2026-63939 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
AI agents map your attack surface to find vulnerabilities like this one.
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