CVE-2026-93868 in Cotonti
Summary
by MITRE • 09/18/2026
Cotonti through 1.0.0 derives password recovery validation tokens from md5(microtime()) in users.passrecover.php, creating a predictable token space of approximately one million values per second. Unauthenticated attackers can read the server Date header, precompute candidate tokens within a narrow time window, and probe them against the passrecover authentication endpoint to reset any account password including administrators.
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Analysis
by VulDB Data Team • 09/18/2026
The vulnerability identified in Cotonti versions up to 1.0.0 represents a critical failure in cryptographic randomness generation during the password recovery process. Specifically, the application utilizes an insecure pseudo-random number generator by deriving validation tokens from the MD5 hash of the current microtime value within the users.passrecover.php script. This approach fundamentally violates security best practices for generating session identifiers or one-time passwords because it relies on a predictable input source that is partially observable to external actors. The resulting token space, while seemingly large due to the millisecond precision of time, is effectively constrained by the predictability of the underlying system clock and the deterministic nature of the MD5 algorithm. This creates a scenario where an attacker can significantly narrow down the possible values for a valid recovery token, transforming what should be a cryptographically secure random value into a brute-forceable sequence with high probability of success within a short timeframe.
From a technical perspective, the core flaw lies in the use of md5(microtime()) as the sole entropy source for generating password reset tokens. Microtime provides time-based data which is easily accessible through standard HTTP headers such as the Date header returned by the web server. By reading this header during an initial interaction with the application, an attacker can determine the approximate timestamp used to generate a token. Since MD5 is a fast cryptographic hash function and does not involve any salt or secret key known only to the server, the output for a given input time is deterministic. Consequently, if an attacker knows the exact second or even millisecond when the password reset request was initiated by a victim, they can precompute millions of potential token values per second. This reduces the attack complexity from exponential to linear relative to the number of milliseconds in the relevant window, making it computationally trivial for modern hardware to exhaust the candidate space and identify the correct token.
The operational impact of this vulnerability is severe, allowing unauthenticated attackers to perform account takeover attacks against any user on the system, including privileged administrators. By exploiting the predictable nature of these tokens, an attacker can intercept or observe a password reset request, determine the time window associated with that event, and then systematically probe the passrecover authentication endpoint using precomputed candidates. Once a valid token is identified through this brute-force mechanism, the attacker gains full control over the targeted account without needing to know the original password or bypass any multi-factor authentication mechanisms that might be in place for login but not for recovery flows. This undermines the integrity of user accounts and can lead to data breaches, unauthorized modifications, and further lateral movement within an organization if administrative credentials are compromised.
This vulnerability aligns with CWE-330: Use of Insufficiently Random Values, as it involves generating values that should be unpredictable using a method that lacks sufficient entropy or secrecy. Furthermore, the exploitation technique falls under MITRE ATT&CK Tactic TA0001 Initial Access and specifically relates to techniques involving credential access through password reset abuse. The lack of server-side rate limiting on the recovery endpoint exacerbates the issue by allowing rapid successive attempts without triggering defensive mechanisms such as account lockouts or CAPTCHA challenges, which are standard mitigations for brute-force attacks in other contexts but were absent here.
To mitigate this vulnerability, immediate remediation is required to replace the insecure token generation mechanism with a cryptographically secure pseudo-random number generator (CSPRNG). The application should utilize functions such as random_bytes() or openssl_random_pseudo_bytes() which draw from operating system entropy sources like /dev/urandom on Unix-like systems. Additionally, password reset tokens must be bound to specific user sessions and have short expiration times to limit the window of opportunity for attackers. Implementing rate limiting on the password recovery endpoint is also essential to prevent rapid automated probing even if token prediction remains partially feasible due to other factors. Finally, ensuring that sensitive operations like password resets require additional verification steps or are logged with detailed audit trails can help in detecting and responding to such abuse attempts effectively.