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CVE-2026-63939 is a Linux kernel KVM vulnerability in AMD SEV/SNP GHCB scratch-area handling. The flaw is caused by computing and storing an incorrect effective length for an in-GHCB scratch area when the scratch region resides in the GHCB shared buffer. Instead of deriving the maximum usable size from the guest-provided start pointer to the end of the shared buffer, the code used a length value that reflected only the minimum required size for request parsing. This behavior was not sufficient for PSC request handling, where KVM must know the full scratch-area extent. As a result, guest-controlled accesses could extend beyond the actual valid bounds of the shared buffer, creating a buffer overflow condition in host-side kernel processing.
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What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
If you can’t patch tonight, do this now.
Patch, then assume compromise.
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
1 sources tracked across advisories and community write-ups. News coverage will land here when it surfaces.
No news coverage yet. Advisories and community discussion only.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.