Vulnerability report

Active exploitation observed Confirmed confidence Not in CISA KEV

CVE-2023-54391

Proxmox Virtual Environment (VE) Proxmox VE 7.0 8.0 Authentication Bypass

Proxmox Server Solutions / Proxmox Virtual Environment (VE) · 7.0 to <= 7.4

Watch CVE-2023-54391 Browse KEV feed
Severity
CVSS 9.3 · Critical
Confidence
Confirmed
Exploit status
Observed in sensors
EPSS
3.1%
First observed
20 Sep 2026
Last observed
10 Oct 2026

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2023-54391 is an unauthenticated vulnerability affecting Proxmox Server Solutions Proxmox Virtual Environment (VE). Proxmox Virtual Environment (VE) 7.0 through 8.0 contains an authentication bypass vulnerability...

Is it exploited?

Yes. Previdian sensors observed exploitation attempts with confirmed confidence. Also confirmed by third-party sources.

Who is affected?

Proxmox Server Solutions / Proxmox Virtual Environment (VE) 7.0 to <= 7.4.

What should we do?

Patch immediately, validate internet-facing exposure, and monitor for matching requests.

Overview

Proxmox Virtual Environment (VE) Proxmox VE 7.0 8.0 Authentication Bypass

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.

Proxmox Server Solutions GmbH Affected
Proxmox Virtual Environment (VE)
Through 7.4 8.0
View vendor advisory (opens in new tab)
Published
01 Sep 2026
Exploitation Reported
01 Sep 2026
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

Tags

linux nuclei_scanner

CVE References

  • CVE Record CVE.org · CVE Record https://www.cve.org/CVERecord?id=CVE-2023-54391
  • Vendor Advisory forum.proxmox.com · Vendor Advisory https://forum.proxmox.com/threads/proxmox-virtual-environment-securit...
  • Patch Commit git.proxmox.com · Patch https://git.proxmox.com/?p=pve-access-control.git;a=commit;h=032e7d6d...
  • Third-Party Advisory — vulncheck.com vulncheck.com · Third-Party Advisory https://www.vulncheck.com/advisories/proxmox-ve-authentication-bypass...
  • Introducing Commit git.proxmox.com · CVE Record https://git.proxmox.com/?p=pve-access-control.git;a=commit;h=0f3d14d6...

Exploitation evidence

Why Previdian marks this CVE as exploited

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploited in the wild

CVE

Recorded 01 Sep 2026

A trusted third party reported exploitation.

Active exploitation observed

Previdian sensor

First observed 20 Sep 2026

Previdian first observed exploitation attempts targeting this vulnerability in our honeypot sensors.

Proof of concept available

Nuclei Templates

Recorded 01 Sep 2026

Public scanner or PoC coverage increases practical exploitability.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian Pro API.

Learn about Pro API access
Source Added
Previdian First 2026-09-01 20:57 UTC
CVE 2026-09-01 22:10 UTC
The Hacker News 2026-09-22 11:32 UTC

Operational indicators for this CVE are listed under Detection.

Sensor telemetry

First-party evidence of exploitation activity

Previdian sensors recorded exploitation attempts targeting this vulnerability. The cards and chart show volume, unique attackers, and daily activity.

7

Attempts observed

4

Unique attacker IPs

4

Attacker countries

BG · CH · DE · YE

4

Sensors observed

CVE-2023-54391 exploitation attempts over the last 29 days

Daily events observed by Previdian sensors

Updated 17 Oct 2026

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1
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1
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0
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0
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19 Sep 25 Sep 1 Oct 7 Oct 17 Oct

First observed 20 Sep 2026 · Last observed 10 Oct 2026

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Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets
User-Agents
Callback hosts
1
7
0

Request targets and User-Agents available in Pro. Callback host details available in Enterprise.

Virtual patch status

No Previdian virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

Attacker IP Indicators

Attacker IP indicators observed · available in Pro and Enterprise.

Sensor-derived attacker IP indicators are available to Pro and Enterprise accounts under Detection and through the Pro API.

Learn about Pro API access

Scanner Artifacts

Scanner and exploit-framework references linked to this CVE.

Scanner Reference Detected
Nuclei https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2023/CVE-2023-54391.yaml 05 Sep 2026

Risk and context

Severity, weaknesses, and research context

CVSS v4.0

9.3 Critical

Potential damage if exploited. Separate from whether attackers are using it.

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

EPSS

3.1%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

Weaknesses

Missing Critical Step in Authentication CWE-304

Recent mention · The Hacker News

Zyxel and Veeam Flaws Under Active Exploitation With Command and SYSTEM Access

Ravie LakshmananSep 22, 2026Vulnerability / Endpoint Security The U.S. Cybersecurity and Infrastructure Security Agency (CISA) on Monday added a now-patched security flaw impacting Zyxel GS1900 series switches to its Known Exploited Vulnerabilities (KEV) catalog, citing...

Read full advisory

All CVSS Scores

CVSS v4.0 9.3 Critical

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

CVSS v3.1 9.8 Critical

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

All Mentions

Recent mention · The Hacker News

Zyxel and Veeam Flaws Under Active Exploitation With Command and SYSTEM Access

The Hacker News · 22 Sep 2026

Ravie LakshmananSep 22, 2026Vulnerability / Endpoint Security The U.S. Cybersecurity and Infrastructure Security Agency (CISA) on Monday added a now-patched security flaw impacting Zyxel GS1900 series switches to its Known Exploited Vulnerabilities (KEV) catalog, citing evidence of active exploitation. The vulnerability, tracked as CVE-2026-7273 (CVSS score: 8.8), is a stack-based buffer overflow vulnerability that could result in arbitrary operating system (OS) command execution. "A stack-based buffer overflow vulnerability in the CGI program of the Zyxel GS1900 series switch firmware...

Recent mention · GreyNoise

Open Season on Kapibala: Attacker Steals Over 18,000 Government Records Through WordPress Exploitation

GreyNoise · 21 Sep 2026

GreyNoise has been tracking malicious use of an IP address since early June 2026 due to its frequent use in scans and attacks against a variety of technologies. We detail a few of the more notable intrusions we observed including the theft of more than 18,000 sensitive records from a western government.

Potential Proof of Concepts

These PoCs are unverified and could contain malware. Use at your own risk.

PVE 7.4 auth-bypass @NebuSec

public · Created 2026-09-01 11:04:00 UTC

Proxmox VE - Default Credentials with TFA Bypass

nuclei · Created Unknown

Timeline

From disclosure to observed exploitation

  1. 11:32 UTC

    KEV confirmed by The Hacker News

    Exploitation attested by an external source

  2. 13:18 UTC

    Indicators of compromise added (4)

    Indicators of compromise recorded

  3. 13:18 UTC

    Observed by Previdian sensors

    Evidence-backed exploitation signal

  4. 04:31 UTC

    Nuclei template available

    Scanner coverage available

  5. 22:29 UTC

    CVE ID assigned

    Previously tracked as VULN-2026-0002

  6. 22:10 UTC

    KEV confirmed by CVE

    Exploitation attested by an external source

  7. 21:59 UTC

    CVE published

    Vulnerability disclosed publicly

  8. 21:23 UTC

    CVE ID reserved

    Identifier reserved by the CNA

  9. 20:57 UTC

    Added to Previdian KEV Feed

    High-confidence, third-party attested exploitation

  10. 11:04 UTC

    Public PoC available

    Public proof-of-concept code published

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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  • Evidence confidence and provenance
  • First-party sensor telemetry
  • PoC and scanner references
  • Affected versions and enrichment
  • Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2023-54391

Sample API response 
{
  "cve_id": "CVE-2023-54391",
  "confidence": "Confirmed",
  "cvss_score": 9.3,
  "cvss_estimated": false,
  "epss_score": 0.03055,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": true
  },
  "sensor_telemetry": { "attempts": 7, "sensors": 4 }
}