CVE-2026-89981

A flaw was found in the Linux kernel, specifically affecting arm64 architectures. When the Memory Tagging Extension (MTE) is disabled, the kernel attempts to read a register (GMID_EL1) that should not be accessed. In a virtualized environment utilizing protected Kernel-based Virtual Machine (pKVM), this can lead to an unhandled instruction error if a CPU is offlined and then brought back online. This issue results in a kernel panic, causing a Denial of Service (DoS) on the host system.

This vulnerability is evaluated as Moderate severity because triggering the fault requires an uncommon combination of platform configurations and privileged operational actions, with the impact restricted to local denial of service. The condition is isolated to 64-bit ARM environments deployed with protected KVM hypervisor extensions when memory tagging features are disabled. An unexpected kernel crash occurs only when a processor core is removed and re-added to the running system, preventing any escalation of privilege or compromise of data confidentiality and integrity.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.