{"id":"CVE-2026-89981","published":"2026-09-16T11:17:09.037","lastModified":"2026-09-16T11:17:09.037","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.","cvssScore":null,"cvssSeverity":null,"cvssVector":null,"cwes":[],"vendors":[],"products":[],"references":[{"url":"https://git.kernel.org/stable/c/5445d64199626974269fcdf347769ad44b0bb53b","tags":[]},{"url":"https://git.kernel.org/stable/c/d2d22ff377cd43f2e9660426ff22e3cd4c534637","tags":[]}],"exploitRefs":[],"hasPoc":false,"ai":null}