In the Linux kernel KVM implementation for ARM64, the routine that injects EL2 exceptions fails to write the ESR_EL2 register for injected nested SError exceptions, while it correctly writes ESR_EL2 for synchronous exceptions. The entry exception handler does not set ESR_ELx for any exception type, so the fault syndrome is dropped. As a result, a guest level‑2 hypervisor that receives a nested SError sees a stale ESR_EL2 value, which can lead to incorrect exception handling inside the guest. This defect can potentially be exploited by a malicious guest to gain privileges or cause instability in the nested environment. Based on the description, it is inferred that this could lead to privilege escalation or destabilization within nested virtual machines.

All Linux kernel builds that include the KVM ARM64 support and have not applied the recent commit that fixes the ESR_EL2 handling are affected. Vendor‑specific information lists the product as Linux:Linux, but specific release numbers or patch levels are not provided in the data, so any unpatched KVM arm64 installation is potentially vulnerable.

The CVSS score is not provided, indicating no readily available exploitation data. The vulnerability is not listed in the CISA KEV catalog. A potential attacker would need a guest with nested virtualization privileges; the attack would involve crafting a nested SError that causes the guest hypervisor to misinterpret the exception syndrome. While no public exploit is documented, the lack of proper exception handling can be leveraged to disrupt the guest or potentially bypass isolation boundaries. The likely attack vector is a malicious guest with nested hypervisor privileges that triggers a nested SError, as inferred from the description. Because the issue lies within host kernel code, the risk is considered moderate to high for environments enabling nested virtualization and should be mitigated as soon as possible.