Review reviewHigh

CVE-2026-63937

Linux

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.

CVSS: 8.8
EPSS: -
CISA KEV: Not listed
Published: 2026.07.20

PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV

Exploit probability-

Technical severityCVSS 8.8

Vulnerability overview

Affected product and versions

Product: Linux
Affected versions: >= 9b54e248d2644be71cb394eb85f31ad99e023a05 < bd232801ef1d1fd985d2d4ca3cd1d888303ca86f, >= 9b54e248d2644be71cb394eb85f31ad99e023a05 < b1dfaa6f7a957726a6800135be3659fbe4bbf2a4, >= 9b54e248d2644be71cb394eb85f31ad99e023a05 < edbbe88f83b524434974e84808d3093199d67c24, >= 9b54e248d2644be71cb394eb85f31ad99e023a05 < c8cc238093ca6c99267032f6cfe78f59389f3157, >= 6.11
Fixed versions: No verified fixed-version field is available yet

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide

1
Identify
Confirm that Linux and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
CWE: Not available