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

> Unauthenticated attackers can bypass authentication and gain root access by supplying an arbitrary tfa-challenge value in the API login endpoint.

- **Severity:** Critical 9.3 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 1 Sep 2026
- **Updated:** 1 Oct 2026
- **Also known as:** GHSA-m457-grcf-698x

## What is CVE-2023-54391?

CVE-2023-54391 is a critical authentication bypass vulnerability in Proxmox Virtual Environment (VE), published on 1 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-304 (Missing Critical Step in Authentication)

## Which versions are affected by CVE-2023-54391?


## How do I fix CVE-2023-54391?

No fix has been published for CVE-2023-54391 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-54391 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-54391 exists.

Public exploit code:

- CVE-2023-54391: Proxmox VE Authentication Bypass RCE Exploit (github_poc): https://github.com/alexand0www/CVE-2023-54391-RCE
- Recovery notes for proxmox advisory ID: PSA-2026-00043-1 (CVE-2023-54391) (github_poc): https://github.com/disqualifier/psa-2026-00043-recovery
- https://github.com/Lewis1766/CVE-2023-54391-POC (github_poc): https://github.com/Lewis1766/CVE-2023-54391-POC
- Proxmox VE - Default Credentials with TFA Bypass (nuclei): http/cves/2023/CVE-2023-54391.yaml

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-54391 and fix it if it is affected.

What it is: CVE-2023-54391 is a critical authentication bypass vulnerability in Proxmox Virtual Environment (VE), published on 1 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-54391 exists.

Affected product: Proxmox Virtual Environment (VE). No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2023-54391/ (Markdown: https://insights.sbomify.com/CVE-2023-54391/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-54391
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-54391
- OSV: https://osv.dev/vulnerability/CVE-2023-54391

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-54391/
Summaries are generated and may contain mistakes; the official description above is the record.