Description
phpMyAdmin through 5.2.3 contains an authentication bypass vulnerability in CustomServer::parseAndValidateAssertionResponse() that never verifies WebAuthn assertion signatures against stored public keys. Attackers holding a victim's MySQL credentials can POST a crafted webauthn_request_response with matching challenge, origin, and rpIdHash to bypass the second factor and gain database privileges.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| phpMyAdmin | phpMyAdmin | ≤ 5.2.3 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | phpmyadmin | No fix yet | — |
| Debian 13 | phpmyadmin | No fix yet | — |
| Debian 12 | phpmyadmin | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | phpmyadmin | No fix yet | — |
| Ubuntu 26.04 LTS | phpmyadmin | No fix yet | — |
| Ubuntu 24.04 LTS | phpmyadmin | No fix yet | — |
| Ubuntu 22.04 LTS | phpmyadmin | No fix yet | — |
Show 4 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 20.04 LTS | phpmyadmin | No fix yet | — |
| Ubuntu Pro 18.04 LTS | phpmyadmin | No fix yet | — |
| Ubuntu Pro 16.04 LTS | phpmyadmin | No fix yet | — |
| Ubuntu Pro 14.04 LTS | phpmyadmin | No fix yet | — |
Advisories 1
- WID-SEC-2026-4278 phpMyAdmin: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 1, 2026
References
- https://github.com/phpmyadmin/phpmyadmin/blob/RELEASE_5_2_3/libraries/classes/WebAuthn/CustomServer.php#L76-L110 technical-description
- https://abraxaslabs.tech/research/PMA-5.2.3-WebAuthn-2FA third-party-advisory
- https://abraxaslabs.tech/research/phpmyadmin-webauthn third-party-advisory
- https://github.com/phpmyadmin/phpmyadmin product
- VulnCheck Advisory: phpMyAdmin through 5.2.3 WebAuthn Two-Factor Authentication Bypass via CustomServer third-party-advisory