In the Linux kernel, the following vulnerability has been resolved: KVM: arm64: Validate the SVE vector length in pkvm_vcpu_init_sve()… (CVE-2026-98638)

The Linux kernel's KVM arm64 subsystem had a vulnerability in the pkvm_vcpu_init_sve() function where only the upper bound of the host-provided sve_max_vl was clamped. This allowed invalid vector lengths to reach sve_state_size_from_vl(), triggering a WARN_ON() condition that is fatal at EL2. Although there was a subsequent test rejecting invalid lengths, it occurred after the macro execution that caused the fault. The fix adds a check with sve_vl_valid() before deriving the state size, ensuring invalid vector lengths are rejected earlier and preventing fatal kernel warnings.

An invalid SVE vector length could cause a fatal kernel warning (WARN_ON()) at EL2 in the KVM arm64 virtualization context, potentially leading to a denial of service of the virtual machine or host system. No information about code execution or privilege escalation is provided.

A fix has been implemented in the Linux kernel to validate the SVE vector length properly in pkvm_vcpu_init_sve(). Users should apply the official kernel updates that include this patch. Since no vendor advisory or patch links are provided, check the Linux kernel mailing lists or official repositories for the patch and update guidance.