KVM: SEV: Compute the correct max length of the in-GHCB scratch area
Summary
| CVE | CVE-2026-63939 |
|---|---|
| State | PUBLISHED |
| Assigner | Linux |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-07-19 16:17:12 UTC |
| Updated | 2026-07-20 15:16:57 UTC |
| 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. |
Risk And Classification
Primary CVSS: v3.1 9.3 CRITICAL from 416baaa9-dc9f-4396-8d5f-8c081fb06d67
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
EPSS: 0.002160000 probability, percentile 0.121220000 (date 2026-07-20)
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | Secondary | 9.3 | CRITICAL | CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H |
| 3.1 | CNA | DECLARED | 9.3 | CRITICAL | CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H |
CVSS v3.1 Breakdown
Attack Vector
LocalAttack Complexity
LowPrivileges Required
NoneUser Interaction
NoneScope
ChangedConfidentiality
HighIntegrity
HighAvailability
HighCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Linux | Linux | affected 9b54e248d2644be71cb394eb85f31ad99e023a05 6ca9400d36005ffdca25f80186bea781c7e1dc4c git | Not specified |
| CNA | Linux | Linux | affected 9b54e248d2644be71cb394eb85f31ad99e023a05 9f0a9e780f02c02d025a190f1885e1d1d73b87bd git | Not specified |
| CNA | Linux | Linux | affected 9b54e248d2644be71cb394eb85f31ad99e023a05 6644565527c4c5f507088b1c9ddf72de47790b68 git | Not specified |
| CNA | Linux | Linux | affected 9b54e248d2644be71cb394eb85f31ad99e023a05 5867d7e202e09f037cefe77f7af4413c7c0fa088 git | Not specified |
| CNA | Linux | Linux | affected 6.11 | Not specified |
| CNA | Linux | Linux | unaffected 6.11 semver | Not specified |
| CNA | Linux | Linux | unaffected 6.12.93 6.12.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.18.35 6.18.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.0.12 7.0.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.1 * original_commit_for_fix | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| git.kernel.org/stable/c/9f0a9e780f02c02d025a190f1885e1d1d73b87bd | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/6ca9400d36005ffdca25f80186bea781c7e1dc4c | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/6644565527c4c5f507088b1c9ddf72de47790b68 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/5867d7e202e09f037cefe77f7af4413c7c0fa088 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.