CVE-2026-85590: Use of Single-factor Authentication in thorsten phpMyFAQ
Description
phpMyFAQ before 4.1.8 contains an authentication bypass vulnerability in its two-factor authentication (TOTP) disable functionality. The removeTwofactorConfig() handler (reachable via POST /api/user/remove-twofactor) verifies only that the user is logged in and that a valid CSRF token is supplied, then disables TOTP without requiring password re-entry or a current TOTP code. The same downgrade is also reachable inline via PUT /api/user/data/update, which accepts a plain twofactor_enabled form field under the same session+CSRF-only guard. An attacker who has hijacked a user's session can silently strip two-factor protection from any account, including administrator accounts, after which password-only authentication succeeds.
CVSS v4.0
Score 7.1high
Affected software
thorsten
phpMyFAQ
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in phpMyFAQ prior to 4.1.8 involves the removeTwofactorConfig() handler and an inline downgrade via the PUT /api/user/data/update endpoint. Both endpoints verify only that the user is logged in and a valid CSRF token is present, but do not require password re-entry or current TOTP code to disable two-factor authentication. This allows an attacker who has hijacked a user's session to silently remove two-factor authentication protection from any account, including administrators, thereby bypassing the intended two-factor security.
Potential Impact
An attacker who has hijacked a user's session can disable two-factor authentication without additional verification, reducing account security to single-factor password authentication. This increases the risk of account compromise, especially for administrator accounts, potentially leading to unauthorized access and control over the phpMyFAQ instance.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, restrict session hijacking risks by securing session management and CSRF protections. Monitor for updates from the vendor regarding an official fix.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-09-04T10:59:00.162Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6a9aada1acd9273b4981d9f9
Added to database: 09/04/2026, 11:38:09 UTC
Last enriched: 09/07/2026, 12:20:19 UTC
Last updated: 10/17/2026, 18:48:23 UTC
Views: 50
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