# CVE-2026-89981: linux: In the Linux kernel, the following vulnerability has been resolved:  arm64: Don't read GMID_EL1 when MTE is disabled...

CVE-2026-89981 is fixed in linux on 1 platform by DEBIAN-CVE-2026-89981 (version 7.2.6-1), released September 23, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-89981
- Priority: Routine
- CVSS: n/a
- EPSS: 0.0020
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 16, 2026

## Description

In the Linux kernel, the following vulnerability has been resolved:  arm64: Don't read GMID_EL1 when MTE is disabled  __cpuinfo_store_cpu() gates the GMID_EL1 read on the raw ID_AA64PFR1_EL1, so it reads the register even when the kernel has disabled MTE (CONFIG_ARM64_MTE=n or arm64.nomte). KVM sets HCR_EL2.TID5 in that case, and pKVM injects an UNDEF the host cannot handle:    Internal error: Oops - Undefined instruction: 0000000002000000 [#1]  SMP   pc : __cpuinfo_store_cpu+0xf4/0x264   Kernel panic - not syncing: Attempted to kill the idle task!  Only pKVM reaches it, and only after a CPU is offlined and brought back online: its CPU_ON relay sets the host HCR before the CPU enters EL1, while plain nVHE sets it at CPUHP_AP_KVM_ONLINE.  Gate the read on the CPU's own ID_AA64PFR1_EL1 with the command-line override applied, and on CONFIG_ARM64_MTE, which no register reflects. The boot CPU stores its registers before init_cpu_features() strips an unsafe override, so clamp against the hardware value here too.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 14 | 7.2.6-1 | [DEBIAN-CVE-2026-89981](https://patchblox.com/security/data/fix/linux/debian-cve-2026-89981.md) | Sep 23, 2026 |

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