{"id":"CVE-2021-47255","state":"PUBLISHED","title":"kvm: LAPIC: Restore guard to prevent illegal APIC register access","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nkvm: LAPIC: Restore guard to prevent illegal APIC register access\n\nPer the SDM, \"any access that touches bytes 4 through 15 of an APIC\nregister may cause undefined behavior and must not be executed.\"\nWorse, such an access in kvm_lapic_reg_read can result in a leak of\nkernel stack contents. Prior to commit 01402cf81051 (\"kvm: LAPIC:\nwrite down valid APIC registers\"), such an access was explicitly\ndisallowed. Restore the guard that was removed in that commit.","publishedAt":"2024-05-21T14:19:50.125Z","updatedAt":"2026-05-11T13:50:57.669Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"01402cf81051f796dac7c60ca11d6147153ca46a","status":"affected","lessThan":"bf99ea52970caeb4583bdba1192c1f9b53b12c84","versionType":"git"},{"version":"01402cf81051f796dac7c60ca11d6147153ca46a","status":"affected","lessThan":"018685461a5b9a9a70e664ac77aef0d7415a3fd5","versionType":"git"},{"version":"01402cf81051f796dac7c60ca11d6147153ca46a","status":"affected","lessThan":"a2aff09807fbe4018c269d3773a629949058b210","versionType":"git"},{"version":"01402cf81051f796dac7c60ca11d6147153ca46a","status":"affected","lessThan":"218bf772bddd221489c38dde6ef8e917131161f6","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/x86/kvm/lapic.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.3","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.3","versionType":"semver"},{"version":"5.4.128","status":"unaffected","lessThanOrEqual":"5.4.*","versionType":"semver"},{"version":"5.10.46","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.12.13","status":"unaffected","lessThanOrEqual":"5.12.*","versionType":"semver"},{"version":"5.13","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/x86/kvm/lapic.c"]}],"references":["https://git.kernel.org/stable/c/bf99ea52970caeb4583bdba1192c1f9b53b12c84","https://git.kernel.org/stable/c/018685461a5b9a9a70e664ac77aef0d7415a3fd5","https://git.kernel.org/stable/c/a2aff09807fbe4018c269d3773a629949058b210","https://git.kernel.org/stable/c/218bf772bddd221489c38dde6ef8e917131161f6"],"weaknesses":[],"ingestedAt":"2026-10-29T19:49:19.404Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2021/47xxx/CVE-2021-47255.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2021-47255","state":"PUBLISHED","datePublished":"2024-05-21T14:19:50.125Z","dateUpdated":"2026-05-11T13:50:57.669Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2024-04-10T18:59:19.539Z"},"containers":{"cna":{"title":"kvm: LAPIC: Restore guard to prevent illegal APIC register access","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nkvm: LAPIC: Restore guard to prevent illegal APIC register access\n\nPer the SDM, \"any access that touches bytes 4 through 15 of an APIC\nregister may cause undefined behavior and must not be executed.\"\nWorse, such an access in kvm_lapic_reg_read can result in a leak of\nkernel stack contents. Prior to commit 01402cf81051 (\"kvm: LAPIC:\nwrite down valid APIC registers\"), such an access was explicitly\ndisallowed. Restore the guard that was removed in that commit."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"01402cf81051f796dac7c60ca11d6147153ca46a","status":"affected","lessThan":"bf99ea52970caeb4583bdba1192c1f9b53b12c84","versionType":"git"},{"version":"01402cf81051f796dac7c60ca11d6147153ca46a","status":"affected","lessThan":"018685461a5b9a9a70e664ac77aef0d7415a3fd5","versionType":"git"},{"version":"01402cf81051f796dac7c60ca11d6147153ca46a","status":"affected","lessThan":"a2aff09807fbe4018c269d3773a629949058b210","versionType":"git"},{"version":"01402cf81051f796dac7c60ca11d6147153ca46a","status":"affected","lessThan":"218bf772bddd221489c38dde6ef8e917131161f6","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/x86/kvm/lapic.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.3","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.3","versionType":"semver"},{"version":"5.4.128","status":"unaffected","lessThanOrEqual":"5.4.*","versionType":"semver"},{"version":"5.10.46","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.12.13","status":"unaffected","lessThanOrEqual":"5.12.*","versionType":"semver"},{"version":"5.13","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/x86/kvm/lapic.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/bf99ea52970caeb4583bdba1192c1f9b53b12c84"},{"url":"https://git.kernel.org/stable/c/018685461a5b9a9a70e664ac77aef0d7415a3fd5"},{"url":"https://git.kernel.org/stable/c/a2aff09807fbe4018c269d3773a629949058b210"},{"url":"https://git.kernel.org/stable/c/218bf772bddd221489c38dde6ef8e917131161f6"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-05-11T13:50:57.669Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"5.4.128"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"5.10.46"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"5.12.13"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"5.13"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2021-47255","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2024-05-21T18:50:43.929512Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2024-06-04T17:14:17.935Z"}},{"title":"CVE Program Container","references":[{"url":"https://git.kernel.org/stable/c/bf99ea52970caeb4583bdba1192c1f9b53b12c84","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/018685461a5b9a9a70e664ac77aef0d7415a3fd5","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/a2aff09807fbe4018c269d3773a629949058b210","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/218bf772bddd221489c38dde6ef8e917131161f6","tags":["x_transferred"]}],"providerMetadata":{"shortName":"CVE","orgId":"af854a3a-2127-422b-91ae-364da2661108","dateUpdated":"2024-08-04T05:32:07.995Z"}}]}}}