Problem Description

It has been discovered that observing response time during user authentication (backend and frontend) can be used to distinguish between existing and non-existing user accounts.

Solution

Update to TYPO3 version 7.6.58 ELTS, 8.7.48 ELTS, 9.5.37 ELTS, 10.4.32 or 11.5.16 that fix the problem described above.

Extension authors of 3rd party TYPO3 extensions providing a custom authentication service should check if the extension is affected by the described problem. Affected extensions must implement new MimicServiceInterface::mimicAuthUser, which simulates corresponding times regular processing would usually take.

Credits

Thanks to Vautia who reported this issue and to TYPO3 core & security team members Oliver Hader who fixed the issue.

General Advice

Follow the recommendations that are given in the TYPO3 Security Guide. Please subscribe to the typo3-announce mailing list.

General Note

All security related code changes are tagged so that you can easily look them up in our review system.