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Findings

Vulnerability · CVE-2023-54391

proxmox virtual_environment Missing Critical Step in Authentication

Published Sep 1, 2026 · corrected/updated Sep 1, 2026 · Proxmox Server Solutions GmbH Proxmox Virtual Environment (VE) · evidence confidence very high

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. VulnCheck canary evidence. Initial-access exploit intelligence.

Grounded briefings

Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.

Executive

CVE-2023-54391 is a unknown public vulnerability record for Proxmox Server Solutions GmbH Proxmox Virtual Environment (VE). CISA lists it as known exploited. Published remediation guidance: Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.

System administrator

Identify whether Proxmox Server Solutions GmbH Proxmox Virtual Environment (VE) is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: Proxmox Server Solutions GmbH Proxmox Virtual Environment (VE). Published remediation guidance: Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.

Security analyst

Signals on file: EPSS 3.1%. CISA lists it as known exploited. Sources contributing to this record: cve_org, epss, vulncheck_kev. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.

Exploitation and remediation

  • Exploitation evidence

    Confirmed in CISA KEV since Sep 1, 2026. Listed in CISA KEV and VulnCheck KEV.

  • Patch and remediation

    Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable.

  • Safe detection guidance

    Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Sep 1, 2026 · VulnCheck KEV

    Detected

    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 a

  2. Sep 1, 2026 · CISA KEV

    Known exploited

    Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable.

Affected

  • vendor Proxmox Server Solutions GmbH Proxmox Virtual Environment (VE)version unspecified

Sources

  • CVE.orgVulnerability recordCVE-2023-54391

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2023-54391

    30-day exploitation probability 3.1%

    first.org
  • VulnCheck KEVConfirmed exploitationCVE-2023-54391

    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

    vulncheck.com

References