Impact
For applications using JWT or session-based authentication (not OIDC), users can input a login string which can cause a denial of service, as parsing it will be too complex.
Here is an example: https://gist.github.com/atomfrede/311f8a9c6eb74c5c5226af0481155207
The vulnerable expression was never officially released. So only when you generated an application from the master branch between 6.8.0 and 6.9.0 your generated application may be vulnerable.
Patches
If you only used official releases you don’t need to patch your application.
Workarounds
If you have created an application from the master branch, you need to adapt the LOGIN_REGEX in Constants.java. If your regex is
^[a-zA-Z0-9!#$&'*+=?^_`{|}~.-]+@?[a-zA-Z0-9-]+(?:\\.[a-zA-Z0-9-]+)*$
you need to change it too
^(?>[a-zA-Z0-9!$&*+=?^_`{|}~.-]+@[a-zA-Z0-9-]+(?:\\.[a-zA-Z0-9-]+)*)|(?>[_.@A-Za-z0-9-]+)$
If you still have ^[_.@A-Za-z0-9-]*$ there is no need to change it, except you would like to support login with + sign (e.g. foo+bar@example.com).
References
- https://owasp.org/www-community/attacks/Regular_expression_Denial_of_Service_-_ReDoS
- https://snyk.io/blog/redos-and-catastrophic-backtracking/