{"api_version":"1","generated_at":"2026-07-24T02:05:45+00:00","cve":"CVE-2026-63939","urls":{"html":"https://cve.report/CVE-2026-63939","api":"https://cve.report/api/cve/CVE-2026-63939.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-63939","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-63939"},"summary":{"title":"KVM: SEV: Compute the correct max length of the in-GHCB scratch area","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SEV: Compute the correct max length of the in-GHCB scratch area\n\nWhen setting the length of the GHCB scratch area, and the area is in the\nGHCB shared buffer, set the effective length of the scratch area to the max\npossible size given the start of the guest-provided pointer, and the end of\nthe shared buffer.\n\nThe code was \"fine\" when first introduced, as KVM doesn't consult the\nlength of the buffer when emulating MMIO, because the passed in @len always\nspecifies the *max* size required.  But for PSC requests, the incoming @len\nis just the minimum length (to process the header), and KVM needs to know\nthe full size of the scratch area to avoid buffer overflows (spoiler alert).\n\nOpportunistically rename @len => @min_len to better reflect its role.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-07-19 16:17:12","updated_at":"2026-07-20 15:16:57"},"problem_types":[],"metrics":[{"version":"3.1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","score":"9.3","severity":"CRITICAL","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","baseScore":9.3,"baseSeverity":"CRITICAL","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"CHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"9.3","severity":"CRITICAL","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","data":{"baseScore":9.3,"baseSeverity":"CRITICAL","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","version":"3.1"}}],"references":[{"url":"https://git.kernel.org/stable/c/9f0a9e780f02c02d025a190f1885e1d1d73b87bd","name":"https://git.kernel.org/stable/c/9f0a9e780f02c02d025a190f1885e1d1d73b87bd","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/6ca9400d36005ffdca25f80186bea781c7e1dc4c","name":"https://git.kernel.org/stable/c/6ca9400d36005ffdca25f80186bea781c7e1dc4c","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/6644565527c4c5f507088b1c9ddf72de47790b68","name":"https://git.kernel.org/stable/c/6644565527c4c5f507088b1c9ddf72de47790b68","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/5867d7e202e09f037cefe77f7af4413c7c0fa088","name":"https://git.kernel.org/stable/c/5867d7e202e09f037cefe77f7af4413c7c0fa088","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-63939","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-63939","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 9b54e248d2644be71cb394eb85f31ad99e023a05 6ca9400d36005ffdca25f80186bea781c7e1dc4c git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 9b54e248d2644be71cb394eb85f31ad99e023a05 9f0a9e780f02c02d025a190f1885e1d1d73b87bd git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 9b54e248d2644be71cb394eb85f31ad99e023a05 6644565527c4c5f507088b1c9ddf72de47790b68 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 9b54e248d2644be71cb394eb85f31ad99e023a05 5867d7e202e09f037cefe77f7af4413c7c0fa088 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.11","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.11 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.93 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.35 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.0.12 7.0.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.1 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"63939","cve":"CVE-2026-63939","epss":"0.002160000","percentile":"0.121220000","score_date":"2026-07-20","updated_at":"2026-07-21 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the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SEV: Compute the correct max length of the in-GHCB scratch area\n\nWhen setting the length of the GHCB scratch area, and the area is in the\nGHCB shared buffer, set the effective length of the scratch area to the max\npossible size given the start of the guest-provided pointer, and the end of\nthe shared buffer.\n\nThe code was \"fine\" when first introduced, as KVM doesn't consult the\nlength of the buffer when emulating MMIO, because the passed in @len always\nspecifies the *max* size required.  But for PSC requests, the incoming @len\nis just the minimum length (to process the header), and KVM needs to know\nthe full size of the scratch area to avoid buffer overflows (spoiler alert).\n\nOpportunistically rename @len => @min_len to better reflect its role."}],"metrics":[{"cvssV3_1":{"baseScore":9.3,"baseSeverity":"CRITICAL","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","version":"3.1"}}],"providerMetadata":{"dateUpdated":"2026-07-20T13:41:41.058Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/6ca9400d36005ffdca25f80186bea781c7e1dc4c"},{"url":"https://git.kernel.org/stable/c/9f0a9e780f02c02d025a190f1885e1d1d73b87bd"},{"url":"https://git.kernel.org/stable/c/6644565527c4c5f507088b1c9ddf72de47790b68"},{"url":"https://git.kernel.org/stable/c/5867d7e202e09f037cefe77f7af4413c7c0fa088"}],"title":"KVM: SEV: Compute the correct max length of the in-GHCB scratch area","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-63939","datePublished":"2026-07-19T14:55:35.743Z","dateReserved":"2026-07-19T07:54:57.022Z","dateUpdated":"2026-07-20T13:41:41.058Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-07-19 16:17:12","lastModifiedDate":"2026-07-20 15:16:57","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","baseScore":9.3,"baseSeverity":"CRITICAL","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"CHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":2.5,"impactScore":6}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"63939","Ordinal":"1","Title":"KVM: SEV: Compute the correct max length of the in-GHCB scratch ","CVE":"CVE-2026-63939","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"63939","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SEV: Compute the correct max length of the in-GHCB scratch area\n\nWhen setting the length of the GHCB scratch area, and the area is in the\nGHCB shared buffer, set the effective length of the scratch area to the max\npossible size given the start of the guest-provided pointer, and the end of\nthe shared buffer.\n\nThe code was \"fine\" when first introduced, as KVM doesn't consult the\nlength of the buffer when emulating MMIO, because the passed in @len always\nspecifies the *max* size required.  But for PSC requests, the incoming @len\nis just the minimum length (to process the header), and KVM needs to know\nthe full size of the scratch area to avoid buffer overflows (spoiler alert).\n\nOpportunistically rename @len => @min_len to better reflect its role.","Type":"Description","Title":"KVM: SEV: Compute the correct max length of the in-GHCB scratch "}]}}}