SB20260720295 - Improper access control in Linux kernel arm64 kvm

Description

This security bulletin contains information about 1 vulnerability.

1) Improper access control (CVE-ID: CVE-2026-63941)

CWE-ID: CWE-284 - Improper Access Control

CVSSv4: 4.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]

The vulnerability allows a local user to bypass intended vector length restrictions for a nested guest.

The vulnerability exists due to improper access control in the KVM arm64 nested virtualization SVE register handling for ZCR_EL2 when restoring SVE context for an L2 guest after handling guest hypervisor updates through ZCR_EL1. A local user can write an uncapped ZCR_EL2 value via ZCR_EL1 to bypass intended vector length restrictions for a nested guest.

The issue affects VHE guest hypervisor scenarios in nested virtualization on arm64 systems with SVE enabled.

Remediation

Install update from vendor's website.

References

• https://git.kernel.org/stable/c/742a9b5ccd8c46caf983ca90c94f855466968e34
• https://git.kernel.org/stable/c/83726330748981372bde86ed5411d7b306612991