CVE-2023-54391Known exploitationNetwork attack vector

Unauthenticated account access via unvalidated TFA challenge

Published Sep 1, 2026 · Updated Sep 3, 2026

Authentication bypass in Proxmox Virtual Environment 7.0 through 7.4 and 8.0 allows remote attackers to access enabled accounts without credentials. The API login handler fails to validate tfa-challenge for users without TFA and treats its presence as grounds to skip password verification. Exposure requires access to API port 8006 and an enabled account without a configured second factor; root@pam meets that condition by default, granting full account access.

CVSS severity9.3
Critical
EPSS probability1.75%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in Proxmox Virtual Environment 7.0 through 7.4 and 8.0 allows remote attackers to access enabled accounts without credentials. The API login handler fails to validate tfa-challenge for users without TFA and treats its presence as grounds to skip password verification. Exposure requires access to API port 8006 and an enabled account without a configured second factor; root@pam meets that condition by default, granting full account access.

The record

CVE
CVE-2023-54391
Published
Sep 1, 2026
Updated
Sep 3, 2026
Vendor
Proxmox Server Solutions GmbH
Product
Proxmox Virtual Environment
Classifications
CWE-304, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 3, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=7.0 <=7.4
  2. Affected versionversion=8.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Proxmox Server Solutions GmbH · Proxmox Virtual Environmentversion=7.0 <=7.4; version=8.0

Published CVSS scores

9.3VulnCheck CNACVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
9.8VulnCheck CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationReported
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-304Missing Critical Step in Authentication
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

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Your stack

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