{"id":"CVE-2026-43265","state":"PUBLISHED","title":"KVM: x86: Ignore -EBUSY when checking nested events from vcpu_block()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: x86: Ignore -EBUSY when checking nested events from vcpu_block()\n\nIgnore -EBUSY when checking nested events after exiting a blocking state\nwhile L2 is active, as exiting to userspace will generate a spurious\nuserspace exit, usually with KVM_EXIT_UNKNOWN, and likely lead to the VM's\ndemise.  Continuing with the wakeup isn't perfect either, as *something*\nhas gone sideways if a vCPU is awakened in L2 with an injected event (or\nworse, a nested run pending), but continuing on gives the VM a decent\nchance of surviving without any major side effects.\n\nAs explained in the Fixes commits, it _should_ be impossible for a vCPU to\nbe put into a blocking state with an already-injected event (exception,\nIRQ, or NMI).  Unfortunately, userspace can stuff MP_STATE and/or injected\nevents, and thus put the vCPU into what should be an impossible state.\n\nDon't bother trying to preserve the WARN, e.g. with an anti-syzkaller\nKconfig, as WARNs can (hopefully) be added in paths where _KVM_ would be\nviolating x86 architecture, e.g. by WARNing if KVM attempts to inject an\nexception or interrupt while the vCPU isn't running.","publishedAt":"2026-05-06T11:28:51.552Z","updatedAt":"2026-05-11T22:21:13.005Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"26844fee6adee9b1557d2279b0506285de9ee82b","status":"affected","lessThan":"78265cd066d73a5cb41c088fcae4a2515e480d97","versionType":"git"},{"version":"26844fee6adee9b1557d2279b0506285de9ee82b","status":"affected","lessThan":"ec3be7dc9391085a2d96700e159d66d1328b7ff6","versionType":"git"},{"version":"26844fee6adee9b1557d2279b0506285de9ee82b","status":"affected","lessThan":"2657439265d34a911886b916ba8be97ecc117d51","versionType":"git"},{"version":"26844fee6adee9b1557d2279b0506285de9ee82b","status":"affected","lessThan":"1e88b5f854bdb469424132e0bb44793ad7a7c20a","versionType":"git"},{"version":"26844fee6adee9b1557d2279b0506285de9ee82b","status":"affected","lessThan":"1c957773063ed3264953597e32990a748381caf6","versionType":"git"},{"version":"26844fee6adee9b1557d2279b0506285de9ee82b","status":"affected","lessThan":"ead63640d4e72e6f6d464f4e31f7fecb79af8869","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/x86/kvm/x86.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.1","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.1","versionType":"semver"},{"version":"6.1.167","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.130","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.77","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.17","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.6","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","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/x86.c"]}],"references":["https://git.kernel.org/stable/c/78265cd066d73a5cb41c088fcae4a2515e480d97","https://git.kernel.org/stable/c/ec3be7dc9391085a2d96700e159d66d1328b7ff6","https://git.kernel.org/stable/c/2657439265d34a911886b916ba8be97ecc117d51","https://git.kernel.org/stable/c/1e88b5f854bdb469424132e0bb44793ad7a7c20a","https://git.kernel.org/stable/c/1c957773063ed3264953597e32990a748381caf6","https://git.kernel.org/stable/c/ead63640d4e72e6f6d464f4e31f7fecb79af8869"],"weaknesses":[],"ingestedAt":"2026-10-29T20:11:57.932Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/43xxx/CVE-2026-43265.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-43265","state":"PUBLISHED","datePublished":"2026-05-06T11:28:51.552Z","dateUpdated":"2026-05-11T22:21:13.005Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-05-01T14:12:55.997Z"},"containers":{"cna":{"title":"KVM: x86: Ignore -EBUSY when checking nested events from vcpu_block()","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: x86: Ignore -EBUSY when checking nested events from vcpu_block()\n\nIgnore -EBUSY when checking nested events after exiting a blocking state\nwhile L2 is active, as exiting to userspace will generate a spurious\nuserspace exit, usually with KVM_EXIT_UNKNOWN, and likely lead to the VM's\ndemise.  Continuing with the wakeup isn't perfect either, as *something*\nhas gone sideways if a vCPU is awakened in L2 with an injected event (or\nworse, a nested run pending), but continuing on gives the VM a decent\nchance of surviving without any major side effects.\n\nAs explained in the Fixes commits, it _should_ be impossible for a vCPU to\nbe put into a blocking state with an already-injected event (exception,\nIRQ, or NMI).  Unfortunately, userspace can stuff MP_STATE and/or injected\nevents, and thus put the vCPU into what should be an impossible state.\n\nDon't bother trying to preserve the WARN, e.g. with an anti-syzkaller\nKconfig, as WARNs can (hopefully) be added in paths where _KVM_ would be\nviolating x86 architecture, e.g. by WARNing if KVM attempts to inject an\nexception or interrupt while the vCPU isn't running."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"26844fee6adee9b1557d2279b0506285de9ee82b","status":"affected","lessThan":"78265cd066d73a5cb41c088fcae4a2515e480d97","versionType":"git"},{"version":"26844fee6adee9b1557d2279b0506285de9ee82b","status":"affected","lessThan":"ec3be7dc9391085a2d96700e159d66d1328b7ff6","versionType":"git"},{"version":"26844fee6adee9b1557d2279b0506285de9ee82b","status":"affected","lessThan":"2657439265d34a911886b916ba8be97ecc117d51","versionType":"git"},{"version":"26844fee6adee9b1557d2279b0506285de9ee82b","status":"affected","lessThan":"1e88b5f854bdb469424132e0bb44793ad7a7c20a","versionType":"git"},{"version":"26844fee6adee9b1557d2279b0506285de9ee82b","status":"affected","lessThan":"1c957773063ed3264953597e32990a748381caf6","versionType":"git"},{"version":"26844fee6adee9b1557d2279b0506285de9ee82b","status":"affected","lessThan":"ead63640d4e72e6f6d464f4e31f7fecb79af8869","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/x86/kvm/x86.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.1","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.1","versionType":"semver"},{"version":"6.1.167","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.130","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.77","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.17","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.6","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","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/x86.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/78265cd066d73a5cb41c088fcae4a2515e480d97"},{"url":"https://git.kernel.org/stable/c/ec3be7dc9391085a2d96700e159d66d1328b7ff6"},{"url":"https://git.kernel.org/stable/c/2657439265d34a911886b916ba8be97ecc117d51"},{"url":"https://git.kernel.org/stable/c/1e88b5f854bdb469424132e0bb44793ad7a7c20a"},{"url":"https://git.kernel.org/stable/c/1c957773063ed3264953597e32990a748381caf6"},{"url":"https://git.kernel.org/stable/c/ead63640d4e72e6f6d464f4e31f7fecb79af8869"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-05-11T22:21:13.005Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1","versionEndExcluding":"6.1.167"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1","versionEndExcluding":"6.6.130"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1","versionEndExcluding":"6.12.77"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1","versionEndExcluding":"6.18.17"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1","versionEndExcluding":"6.19.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1","versionEndExcluding":"7.0"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}