CVE-2026-63939
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.
Affected versions
Linux kernel versions
6.11
and later are affected. Fixed in
6.12.93,
6.18.35,
7.0.12,
7.1
and their respective stable series.
References
4 totalFrequently asked questions
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What is CVE-2026-63939?
CVE-2026-63939 is a unscored severity Linux kernel vulnerability . It affects Linux kernel versions from 6.11 onward and has been patched in 6.12.93, 6.18.35, 7.0.12 and others. CVE-2026-63939 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
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Is there a patch available for CVE-2026-63939?
Yes — CVE-2026-63939 has been patched. Fixed versions include 6.12.93, 6.18.35, 7.0.12 and others. If you are running Linux kernel 6.11 or later up to the fix versions, apply the relevant patch for your kernel branch.
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Is CVE-2026-63939 actively exploited?
No — CVE-2026-63939 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.