CVE-2023-4155: Sev-es / sev-snp vmgexit double fetch vulnerability

Vulnerability summary

CVE-2023-4155 is a medium (CVSS 5.6) vulnerability in fedoraproject fedora. EPSS estimates a 0.17% chance of exploitation in the next 30 days, higher than 6.3% of scored vulnerabilities.

Timeline

1. 13-09-2023
   PublishedVulnerability first disclosed.
2. 27-02-2025
   Last modifiedVulnerability information updated.

Description

A flaw was found in KVM AMD Secure Encrypted Virtualization (SEV) in the Linux kernel. A KVM guest using SEV-ES or SEV-SNP with multiple vCPUs can trigger a double fetch race condition vulnerability and invoke the `VMGEXIT` handler recursively. If an attacker manages to call the handler multiple times, they can trigger a stack overflow and cause a denial of service or potentially guest-to-host escape in kernel configurations without stack guard pages (`CONFIG_VMAP_STACK`).

• CWE-367Time-of-check Time-of-use (TOCTOU) Race ConditionThe product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.