{"id":"CVE-2026-89981","state":"PUBLISHED","title":"arm64: Don't read GMID_EL1 when MTE is disabled","description":"In the Linux kernel, the following vulnerability has been resolved:\n\narm64: Don't read GMID_EL1 when MTE is disabled\n\n__cpuinfo_store_cpu() gates the GMID_EL1 read on the raw\nID_AA64PFR1_EL1, so it reads the register even when the kernel has\ndisabled MTE (CONFIG_ARM64_MTE=n or arm64.nomte). KVM sets HCR_EL2.TID5\nin that case, and pKVM injects an UNDEF the host cannot handle:\n\n  Internal error: Oops - Undefined instruction: 0000000002000000 [#1]  SMP\n  pc : __cpuinfo_store_cpu+0xf4/0x264\n  Kernel panic - not syncing: Attempted to kill the idle task!\n\nOnly pKVM reaches it, and only after a CPU is offlined and brought back\nonline: its CPU_ON relay sets the host HCR before the CPU enters EL1,\nwhile plain nVHE sets it at CPUHP_AP_KVM_ONLINE.\n\nGate the read on the CPU's own ID_AA64PFR1_EL1 with the command-line\noverride applied, and on CONFIG_ARM64_MTE, which no register reflects.\nThe boot CPU stores its registers before init_cpu_features() strips an\nunsafe override, so clamp against the hardware value here too.","publishedAt":"2026-09-16T10:32:58.056Z","updatedAt":"2026-10-19T08:55:55.850Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"f35abcbb8a084db4c24b66ccc8db0405c08e2f61","status":"affected","lessThan":"d2d22ff377cd43f2e9660426ff22e3cd4c534637","versionType":"git"},{"version":"f35abcbb8a084db4c24b66ccc8db0405c08e2f61","status":"affected","lessThan":"5445d64199626974269fcdf347769ad44b0bb53b","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/arm64/include/asm/cpu.h","arch/arm64/include/asm/cpufeature.h","arch/arm64/kernel/cpufeature.c","arch/arm64/kernel/cpuinfo.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"7.0","status":"affected"},{"version":"0","status":"unaffected","lessThan":"7.0","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/include/asm/cpu.h","arch/arm64/include/asm/cpufeature.h","arch/arm64/kernel/cpufeature.c","arch/arm64/kernel/cpuinfo.c"]}],"references":["https://git.kernel.org/stable/c/d2d22ff377cd43f2e9660426ff22e3cd4c534637","https://git.kernel.org/stable/c/5445d64199626974269fcdf347769ad44b0bb53b"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:26.108Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/89xxx/CVE-2026-89981.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-89981","state":"PUBLISHED","datePublished":"2026-09-16T10:32:58.056Z","dateUpdated":"2026-10-19T08:55:55.850Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-11T19:38:34.779Z"},"containers":{"cna":{"title":"arm64: Don't read GMID_EL1 when MTE is disabled","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\narm64: Don't read GMID_EL1 when MTE is disabled\n\n__cpuinfo_store_cpu() gates the GMID_EL1 read on the raw\nID_AA64PFR1_EL1, so it reads the register even when the kernel has\ndisabled MTE (CONFIG_ARM64_MTE=n or arm64.nomte). KVM sets HCR_EL2.TID5\nin that case, and pKVM injects an UNDEF the host cannot handle:\n\n  Internal error: Oops - Undefined instruction: 0000000002000000 [#1]  SMP\n  pc : __cpuinfo_store_cpu+0xf4/0x264\n  Kernel panic - not syncing: Attempted to kill the idle task!\n\nOnly pKVM reaches it, and only after a CPU is offlined and brought back\nonline: its CPU_ON relay sets the host HCR before the CPU enters EL1,\nwhile plain nVHE sets it at CPUHP_AP_KVM_ONLINE.\n\nGate the read on the CPU's own ID_AA64PFR1_EL1 with the command-line\noverride applied, and on CONFIG_ARM64_MTE, which no register reflects.\nThe boot CPU stores its registers before init_cpu_features() strips an\nunsafe override, so clamp against the hardware value here too."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"f35abcbb8a084db4c24b66ccc8db0405c08e2f61","status":"affected","lessThan":"d2d22ff377cd43f2e9660426ff22e3cd4c534637","versionType":"git"},{"version":"f35abcbb8a084db4c24b66ccc8db0405c08e2f61","status":"affected","lessThan":"5445d64199626974269fcdf347769ad44b0bb53b","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/arm64/include/asm/cpu.h","arch/arm64/include/asm/cpufeature.h","arch/arm64/kernel/cpufeature.c","arch/arm64/kernel/cpuinfo.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"7.0","status":"affected"},{"version":"0","status":"unaffected","lessThan":"7.0","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/include/asm/cpu.h","arch/arm64/include/asm/cpufeature.h","arch/arm64/kernel/cpufeature.c","arch/arm64/kernel/cpuinfo.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/d2d22ff377cd43f2e9660426ff22e3cd4c534637"},{"url":"https://git.kernel.org/stable/c/5445d64199626974269fcdf347769ad44b0bb53b"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T08:55:55.850Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"7.0","versionEndExcluding":"7.2.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"7.0","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}