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CVE-2026-63938

CRITICAL 9.3

Published 2026-07-19 · Last modified 2026-07-20

In the Linux kernel, the following vulnerability has been resolved: KVM: SEV: Check PSC request indices against the actual size of the buffer When processing Page State Change (PSC) requests, validate the PSC buffer against the effective size of the scratch area, which could be less than the maximum size if the guest provided a pointer that isn't exactly at the start of the GHCB shared buffer.

ELEVATED IMPACT

Severe if exploited (CVSS 9.3), but no known exploitation and low modeled probability. Patch on a normal cadence.

Exploitation likelihood

0.2%chance of exploitation in 30 days · 8th percentile

○ In CISA KEV ○ Public exploit / PoC

Impact if exploited

9.3CVSS 3.1 · CRITICAL

  • ConfidentialityHigh
  • IntegrityHigh
  • AvailabilityHigh

What an attacker needs

  • ⚠Access: Requires local access to the host
  • ✓Privileges: No account or privileges required
  • ✓User interaction: No user interaction needed
  • ✓Complexity: No special conditions — reliably repeatable

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept & exploit code

Test against your own equipment

curl -s https://vulnpedia.com/cve/CVE-2026-63938/poc.jsonMachine-readable PoC index for this CVE (for automation).

Listed for defensive triage, patch verification, and authorized testing on systems you own. Machine-readable: /cve/CVE-2026-63938/poc.json

Affected

Vendors Linux

Products Linux

Weakness (CWE)

Not classified.

CVSS vector

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

All CVSS metrics

  • CRITICAL 9.3 v3.1 · CNA Primary
    CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
  • CRITICAL 9.3 v3.1 · NVD Secondary
    CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

References

Technical & other

Sources: NVD · CVE.org · EPSS