# CVE-2023-54391

## Summary

- **CVE ID:** CVE-2023-54391
- **Severity:** CRITICAL
- **CVSS Score:** 9.8 (CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N)
- **CWE:** CWE-304
- **Published:** Sep 1, 2026
- **Last Modified:** Sep 3, 2026

## Description

Proxmox Virtual Environment (VE) 7.0 through 8.0 contains an authentication bypass vulnerability in libpve-access-control before 8.0.4 that allows unauthenticated attackers to authenticate as any existing enabled user without a configured second factor by supplying an arbitrary tfa-challenge value in the API login endpoint. Attackers can send a POST request to the access ticket API endpoint with any value in the tfa-challenge parameter to completely skip password verification, gaining unauthorized access including to the root@pam account. All affected releases are end of life.

## Affected Products

- Proxmox Server Solutions GmbH — Proxmox Virtual Environment (VE) (7.0)
- Proxmox Server Solutions GmbH — Proxmox Virtual Environment (VE) (8.0)

## References

- [CNA](https://forum.proxmox.com/threads/proxmox-virtual-environment-security-advisories.149331/page-4#post-867929)
- [CNA](https://git.proxmox.com/?p=pve-access-control.git;a=commit;h=032e7d6d441f89a48cadfd7f47e957c8a561c022)
- [CNA](https://www.vulncheck.com/advisories/proxmox-ve-authentication-bypass-via-tfa-challenge-parameter)
- [CNA](https://git.proxmox.com/?p=pve-access-control.git;a=commit;h=0f3d14d6be4d9f23e511701696a529ef3b7ffd61)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 1.75%
- **EPSS Percentile:** 76.5

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._