CVE-2023-54391 — Proxmox Virtual Environment (VE) 7

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 t

01What is this vulnerability?

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…

02Affected products

No structured affected-product list available — see references below for vendor advisories.

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2026-09-01T22:17:10.283
• Last modified: 2026-09-08T20:18:59.270

09References

• forum.proxmox.com — https://forum.proxmox.com/threads/proxmox-virtual-environment-security-advisorie…
• git.proxmox.com — https://git.proxmox.com/?p=pve-access-control.git;a=commit;h=032e7d6d441f89a48ca…
• git.proxmox.com — https://git.proxmox.com/?p=pve-access-control.git;a=commit;h=032e7d6d441f89a48ca…
• git.proxmox.com — https://git.proxmox.com/?p=pve-access-control.git;a=commit;h=032e7d6d441f89a48ca…
• git.proxmox.com — https://git.proxmox.com/?p=pve-access-control.git;a=commit;h=032e7d6d441f89a48ca…
• git.proxmox.com — https://git.proxmox.com/?p=pve-access-control.git;a=commit;h=0f3d14d6be4d9f23e51…
• www.vulncheck.com — https://www.vulncheck.com/advisories/proxmox-ve-authentication-bypass-via-tfa-ch…