Piwigo is a full featured open source photo gallery application for the web. In Piwigo 15.6.0, using the password reset function allows sending a password-reset URL by entering an existing username or email address. However, the hostname used to construct this URL is taken from the HTTP requests Host header and is not validated at all. Therefore, an attacker can send a password-reset URL with a modified hostname to an existing user whose username or email the attacker knows or guesses. This issue has been patched in version 15.7.0.
The product contains a mechanism for users to recover or change their passwords without knowing the original password, but the mechanism is weak.
It is common for an application to have a mechanism that provides a means for a user to gain access to their account in the event they forget their password. Very often the password recovery mechanism is weak, which has the effect of making it more likely that it would be possible for a person other than the legitimate system user to gain access to that user’s account. Weak password recovery schemes completely undermine a strong password authentication scheme. This weakness may be that the security question is too easy to guess or find an answer to (e.g. because the question is too common, or the answers can be found using social media). Or there might be an implementation weakness in the password recovery mechanism code that may for instance trick the system into e-mailing the new password to an e-mail account other than that of the user. There might be no throttling done on the rate of password resets so that a legitimate user can be denied service by an attacker if an attacker tries to recover their password in a rapid succession. The system may send the original password to the user rather than generating a new temporary password. In summary, password recovery functionality, if not carefully designed and implemented can often become the system’s weakest link that can be misused in a way that would allow an attacker to gain unauthorized access to the system.