The DoLogin Security plugin for WordPress is vulnerable to Authentication Bypass via Insufficient Randomness in all versions up to, and including, 4.3. The vulnerability exists because dologins::rrand() seeds the Mersenne Twister with mt_srand((double) microtime() * 1000000) — discarding the integer-seconds component of microtime() and constraining the seed to a range of approximately 10^6 values (~20 bits of entropy) — after which every character of the 32-character magic-link token is drawn sequentially with mt_rand(), making the entire token a deterministic function of that seed. Because Pswdless::try_login() is registered on the unauthenticated init hook, resolves the target account by the auto-increment numeric ID embedded in the ?dologin=<id>.<hash> parameter, performs the hash comparison using a non-constant-time != operator, and then calls wp_set_auth_cookie() directly — never passing through wp_authenticate() and therefore never triggering the plugins own Auth::_has_login_err() lockout — an unauthenticated attacker can brute-force the ~10^6-candidate seed space to reconstruct an active passwordless login token and authenticate as any targeted user, including administrators, without a password. Exploitation requires that a valid, unexpired passwordless login link (active for up to 7 days) exists for the target account at the time of the attack, and that the numeric link ID is known or guessable from the auto-increment primary key.
Weakness
The product uses a Pseudo-Random Number Generator (PRNG) in a security context, but the PRNG’s algorithm is not cryptographically strong.
Extended Description
When a non-cryptographic PRNG is used in a cryptographic context, it can expose the cryptography to certain types of attacks. Often a pseudo-random number generator (PRNG) is not designed for cryptography. Sometimes a mediocre source of randomness is sufficient or preferable for algorithms that use random numbers. Weak generators generally take less processing power and/or do not use the precious, finite, entropy sources on a system. While such PRNGs might have very useful features, these same features could be used to break the cryptography.
Potential Mitigations
References
- https://plugins.trac.wordpress.org/browser/dologin/tags/4.3/src/pswdless.cls.php#L197
- https://plugins.trac.wordpress.org/browser/dologin/tags/4.3/src/pswdless.cls.php#L27
- https://plugins.trac.wordpress.org/browser/dologin/tags/4.3/src/pswdless.cls.php#L86
- https://plugins.trac.wordpress.org/browser/dologin/tags/4.3/src/s.cls.php#L240
- https://www.wordfence.com/threat-intel/vulnerabilities/id/16bce371-b524-48eb-8537-3f9df802abd3?source=cve