{"id":"CVE-2026-89917","state":"PUBLISHED","title":"KVM: arm64: Handle VNCR TLB invalidation race with vcpu_put() VNCR unmapping","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: arm64: Handle VNCR TLB invalidation race with vcpu_put() VNCR unmapping\n\nWhile VNCR TLB invalidation always occurs under the MMU lock,\nvcpu_put() doesn't, while it unmaps the VNCR page.\n\nThe problem is that the invalidation evaluates vncr_tlb::cpu to\ndecide whether an unmapping needs to take place (cpu != -1) before\nperforming it. On the other hand, this_cpu_reset_vncr_fixmap()\nunconditionally unmaps if L1_VNCR_MAPPED is set.\n\nThese two obviously can race, with a TOCTOU pattern on the TLBI\npath, and a BUG_ON() on the vcpu_put() path. And the two can end-up\ncalling vncr_fixmap(-1), with extra lethal effects.\n\nMove the reset of vncr_tlb::cpu to -1 to a common function, and make\nthis update atomic so that only a single thread can reset the field\nand perform the corresponding unmap. The vcpu_put() still need to\nunconditionally unmap the current VNCR to close another ugly race.\n\nFinally, the assignment of vncr_tlb::cpu is moved to be kept in sync\nwith the actual mapping, similar to L1_VNCR_MAPPED being set.","publishedAt":"2026-09-16T10:32:12.629Z","updatedAt":"2026-10-19T08:54:51.694Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"7270cc9157f474dfc46750a34c9d7defc686b2eb","status":"affected","lessThan":"5cbd8761d001c11ada73b1753d772c4745a70e72","versionType":"git"},{"version":"7270cc9157f474dfc46750a34c9d7defc686b2eb","status":"affected","lessThan":"9065c1261f8a05c6a7a2d90048c7c0665ab2896d","versionType":"git"},{"version":"7270cc9157f474dfc46750a34c9d7defc686b2eb","status":"affected","lessThan":"38640bc32be3fcf9526d477155bc19d3f146231f","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/arm64/kvm/nested.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.16","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.16","versionType":"semver"},{"version":"6.18.52","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.5","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/arm64/kvm/nested.c"]}],"references":["https://git.kernel.org/stable/c/5cbd8761d001c11ada73b1753d772c4745a70e72","https://git.kernel.org/stable/c/9065c1261f8a05c6a7a2d90048c7c0665ab2896d","https://git.kernel.org/stable/c/38640bc32be3fcf9526d477155bc19d3f146231f"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:26.108Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/89xxx/CVE-2026-89917.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-89917","state":"PUBLISHED","datePublished":"2026-09-16T10:32:12.629Z","dateUpdated":"2026-10-19T08:54:51.694Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-11T19:38:34.775Z"},"containers":{"cna":{"title":"KVM: arm64: Handle VNCR TLB invalidation race with vcpu_put() VNCR unmapping","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: arm64: Handle VNCR TLB invalidation race with vcpu_put() VNCR unmapping\n\nWhile VNCR TLB invalidation always occurs under the MMU lock,\nvcpu_put() doesn't, while it unmaps the VNCR page.\n\nThe problem is that the invalidation evaluates vncr_tlb::cpu to\ndecide whether an unmapping needs to take place (cpu != -1) before\nperforming it. On the other hand, this_cpu_reset_vncr_fixmap()\nunconditionally unmaps if L1_VNCR_MAPPED is set.\n\nThese two obviously can race, with a TOCTOU pattern on the TLBI\npath, and a BUG_ON() on the vcpu_put() path. And the two can end-up\ncalling vncr_fixmap(-1), with extra lethal effects.\n\nMove the reset of vncr_tlb::cpu to -1 to a common function, and make\nthis update atomic so that only a single thread can reset the field\nand perform the corresponding unmap. The vcpu_put() still need to\nunconditionally unmap the current VNCR to close another ugly race.\n\nFinally, the assignment of vncr_tlb::cpu is moved to be kept in sync\nwith the actual mapping, similar to L1_VNCR_MAPPED being set."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"7270cc9157f474dfc46750a34c9d7defc686b2eb","status":"affected","lessThan":"5cbd8761d001c11ada73b1753d772c4745a70e72","versionType":"git"},{"version":"7270cc9157f474dfc46750a34c9d7defc686b2eb","status":"affected","lessThan":"9065c1261f8a05c6a7a2d90048c7c0665ab2896d","versionType":"git"},{"version":"7270cc9157f474dfc46750a34c9d7defc686b2eb","status":"affected","lessThan":"38640bc32be3fcf9526d477155bc19d3f146231f","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/arm64/kvm/nested.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.16","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.16","versionType":"semver"},{"version":"6.18.52","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.5","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/arm64/kvm/nested.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/5cbd8761d001c11ada73b1753d772c4745a70e72"},{"url":"https://git.kernel.org/stable/c/9065c1261f8a05c6a7a2d90048c7c0665ab2896d"},{"url":"https://git.kernel.org/stable/c/38640bc32be3fcf9526d477155bc19d3f146231f"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T08:54:51.694Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.16","versionEndExcluding":"6.18.52"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.16","versionEndExcluding":"7.2.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.16","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}