KVM: SEV: Compute the correct max length of the in-GHCB scratch area (Linux Linux)

CVE-2026-63939
CRITICAL 9.3

At a glance

Source
NVD
EPSS
EPSS 0.20 % · percentile 10 ()
State
PUBLISHED
Published
Updated
Assigner
Linux
NVD status
Analyzed

Description

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.

Weaknesses (CWE)

  • CWE-122 — Heap-based Buffer Overflow

References

Scores

VersionScoreVectorScored by
CVSS 3.1CRITICAL 9.3CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:HLinux
CVSS 3.1CRITICAL 9.3CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:HNVD · 416baaa9-dc9f-4396-8d5f-8c081fb06d67 (Secondary)

European references

CERT-FR advisories

Affected configurations (NVD CPE)

Affected products

ProductVersions
Linux · Linuxaffected 9b54e248d2644be71cb394eb85f31ad99e023a05 < 6ca9400d36005ffdca25f80186bea781c7e1dc4c ; affected 9b54e248d2644be71cb394eb85f31ad99e023a05 < 9f0a9e780f02c02d025a190f1885e1d1d73b87bd ; affected 9b54e248d2644be71cb394eb85f31ad99e023a05 < 6644565527c4c5f507088b1c9ddf72de47790b68 ; affected 9b54e248d2644be71cb394eb85f31ad99e023a05 < 5867d7e202e09f037cefe77f7af4413c7c0fa088
Linux · Linuxaffected 6.11 ; unaffected 0 < 6.11 ; unaffected 6.12.93 ≤ 6.12.* ; unaffected 6.18.35 ≤ 6.18.* ; unaffected 7.0.12 ≤ 7.0.* ; unaffected 7.1 ≤ *

Sources

SourceLicence
CVE List (CVEProject cvelistV5)CVE Program Terms of Use
EPSS (FIRST.org)FIRST — attribution requested
ENISA EUVDENISA — reproduction authorised, source acknowledged
CERT-FR (ANSSI)Licence Ouverte / Etalab 2.0
NVD (NIST) via fkie-cad/nvd-json-data-feedsPublic domain — this product uses data from the NVD API but is not endorsed or certified by the NVD