CVE-2025-40931 in Apache::Session::Generate::MD5
Summary
by MITRE • 03/05/2026
Apache::Session::Generate::MD5 versions through 1.94 for Perl create insecure session id.
Apache::Session::Generate::MD5 generates session ids insecurely. The default session id generator returns a MD5 hash seeded with the built-in rand() function, the epoch time, and the PID. The PID will come from a small set of numbers, and the epoch time may be guessed, if it is not leaked from the HTTP Date header. The built-in rand function is unsuitable for cryptographic usage. Predicable session ids could allow an attacker to gain access to systems.
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Analysis
by VulDB Data Team • 03/10/2026
The vulnerability identified as CVE-2025-40931 affects Apache::Session::Generate::MD5 versions through 1.94 in Perl applications, presenting a critical security weakness in session management infrastructure. This flaw resides in the session identifier generation mechanism that underpins web application authentication systems, where predictable session tokens can be exploited by malicious actors to hijack user sessions and gain unauthorized access to protected resources. The vulnerability stems from the use of insecure random number generation techniques that fail to meet cryptographic security requirements essential for maintaining session integrity and user authentication.
The technical implementation of this vulnerability demonstrates a fundamental flaw in entropy generation within the session ID creation process. The MD5 hash function operates on a seed composed of three primary components: the built-in rand() function, epoch time, and process ID. The rand() function, which is inherently unsuitable for cryptographic purposes, provides minimal entropy and predictable output patterns that can be easily reverse-engineered by attackers. Additionally, the process ID values are drawn from a limited range of possible numbers, while the epoch time can often be guessed or derived from network timing information, particularly when the HTTP Date header is not properly obfuscated or when time synchronization is predictable. This combination of factors creates a highly predictable session generation algorithm that fails to provide the cryptographic security necessary for modern web applications.
The operational impact of this vulnerability extends beyond simple session hijacking to encompass broader system compromise and data integrity threats. Attackers who can predict session identifiers gain unauthorized access to user accounts, potentially leading to data breaches, privilege escalation, and unauthorized system modifications. The vulnerability is particularly dangerous in environments where session tokens are transmitted over unencrypted channels or where attackers can observe session creation patterns. This weakness directly violates security principles established in industry standards such as CWE-330, which addresses insufficient entropy in random number generation, and aligns with ATT&CK techniques related to credential access and privilege escalation. The vulnerability affects any system relying on Apache::Session::Generate::MD5 for session management, particularly web applications built on Perl frameworks that utilize this module for authentication token generation.
Mitigation strategies for CVE-2025-40931 require immediate attention through multiple approaches to address the root cause of insecure session generation. Organizations should upgrade to Apache::Session::Generate::MD5 version 1.95 or later, which implements proper cryptographic random number generation techniques. Alternative solutions include implementing session ID generation using cryptographically secure random number generators such as /dev/urandom on Unix-like systems or Windows CryptoAPI functions on Windows platforms. Security measures should also incorporate proper session management practices including secure cookie attributes, session timeout configurations, and regular session token rotation. Network-level protections such as HTTP Strict Transport Security enforcement and proper header configuration can help prevent timing attacks and information leakage that might aid attackers in predicting session identifiers. System administrators should also implement monitoring for unusual session creation patterns and consider implementing additional authentication layers such as multi-factor authentication to provide defense-in-depth against session hijacking attacks. The vulnerability underscores the critical importance of cryptographic best practices in session management and highlights the need for regular security auditing of application components that handle authentication and authorization functions.