CVE-2026-63939KVM: SEV: Compute the correct max length of the in-GHCB scratch area
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 9.3 CRITICAL (v3.1, CNA)CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
- Weakness (CWE)
- Not given
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Linux
- NVD analysis
- Awaiting Analysis
- Record last updated
- Oct 16, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Linux Linux linux:linux (from the name) | 9b54e248d2644be71cb394eb85f31ad99e023a05 builds before 6ca9400d36005ffdca25f80186bea781c7e1dc4c; from 9b54e248d2644be71cb394eb85f31ad99e023a05 before 9f0a9e780f02c02d025a190f1885e1d1d73b87bd; from 9b54e248d2644be71cb394eb85f31ad99e023a05 before 6644565527c4c5f507088b1c9ddf72de47790b68; from 9b54e248d2644be71cb394eb85f31ad99e023a05 before 5867d7e202e09f037cefe77f7af4413c7c0fa088 | CNA record |
References
- https://git.kernel.org/stable/c/6ca9400d36005ffdca25f80186bea781c7e1dc4c
- https://git.kernel.org/stable/c/9f0a9e780f02c02d025a190f1885e1d1d73b87bd
- https://git.kernel.org/stable/c/6644565527c4c5f507088b1c9ddf72de47790b68
- https://git.kernel.org/stable/c/5867d7e202e09f037cefe77f7af4413c7c0fa088
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.