What’s Vulnerable › Vulnerabilities

CVE-2023-54391: Proxmox VE 7.0-8.0 Authentication Bypass via tfa-challenge Parameter

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 3.0% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-09-01 · updated 2026-09-08
• Weakness: CWE-304

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): from 7.0 through 7.4; 8.0

References

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

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