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.
References7
- forum.proxmox.com/threads/proxmox-virtual-environment-security-…
- git.proxmox.com/?p=pve-access-control.git;a=commit;h=032e7d6d44…
- git.proxmox.com/?p=pve-access-control.git;a=commit;h=032e7d6d44…
- git.proxmox.com/?p=pve-access-control.git;a=commit;h=032e7d6d44…
- git.proxmox.com/?p=pve-access-control.git;a=commit;h=032e7d6d44…
- git.proxmox.com/?p=pve-access-control.git;a=commit;h=0f3d14d6be…
- www.vulncheck.com/advisories/proxmox-ve-authentication-bypass-v…
Metrics
- CVSS 3.1
-
9.8
CRITICAL
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - CVSS 4.0
-
9.3
CRITICAL
Score source: CNA
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - EPSS — exploit probability
- 3% percentile: 88 · as of 8 November 2026
- CWE
- CWE-304
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.