Secunia

Chinchilla has reported a weakness in phpBB, which potentially can be exploited by malicious people to change other user's passwords.

The weakness is caused due to the "gen_rand_string()" function generating predictable random numbers. This can e.g. be exploited to change a user's password via the "I forgot my password" functionality by sending a large amount of requests attempting to brute force the validation ID (in worst case 1000000).

Successful exploitation requires knowledge of a user's username and e-mail address (e-mail address not visible by default to other users).

Some other issues which may be security related have also been reported by the vendor.

The weakness has been reported in version 2.0.19 and prior. Other versions may also be affected.

Solution
Update to version 2.0.20.
Further details available in Customer Area

Provided and/or discovered by
Chinchilla

Changelog
Further details available in Customer Area

Original Advisory
http://www.r-security.net/tutorials/view/readtutorial.php?id=4

Deep Links
Links available in Customer Area