CVE Catalog

CVE-2026-63937

HighCVSS 8.8
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.16%

6th percentile - higher than 6% of all known CVEs

Summary

In the Linux kernel, a vulnerability was found in the KVM SEV component due to missing READ_ONCE() when reading entries/indices from the guest-accessible Page State Change (PSC) buffer. This allows a TOCTOU (Time-of-Check Time-of-Use) attack by a malicious guest.

Risk Assessment

The risk is that a malicious guest VM can manipulate the PSC buffer data between check and use, potentially leading to unauthorized page state changes, privilege escalation, or isolation bypass.

Recommendation

Immediately update the Linux kernel to a version containing the fix (commit with READ_ONCE()). Monitor official security advisories from your distribution and apply the patch when available.

Other vulnerabilities in Linux kernel

See all
Original NVD description (English source)

In the Linux kernel, the following vulnerability has been resolved: KVM: SEV: Use READ_ONCE() when reading entries/indices from PSC buffer Use READ_ONCE() when reading entries/indices from the guest-accessible Page State Change buffer to defend against TOCTOU bugs. Don't bother with READ_ONCE()/WRITE_ONCE() for cases where KVM is writing (and not consuming the result!), as the guest isn't supposed to touch the buffer while it's being processed. I.e. using READ_ONCE() is all about protecting against misbehaving guests.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS