CVE-2025-40925 identifies a security vulnerability in the BLUEFEET Starch software, specifically affecting versions 0.14 and earlier, including version 0.01. The vulnerability arises from the insecure generation of session identifiers (session IDs). The default session ID generator uses a SHA-1 hash function seeded with predictable inputs: a counter, the epoch time, the built-in Perl rand() function, the process ID (PID), and internal Perl reference addresses. Each of these components contributes to the predictability of the session IDs. The PID is drawn from a limited range of values, and the epoch time can be approximated or inferred, especially if leaked via HTTP Date headers. The built-in rand() function in Perl is not cryptographically secure, further weakening the randomness of the session ID. The use of SHA-1, which is considered deprecated for cryptographic security, compounds the risk. Because session IDs are used to maintain authenticated user sessions, their predictability can allow an attacker to guess or forge valid session tokens, leading to unauthorized access to user accounts or systems. This vulnerability falls under CWE-340 (Generation of Predictable Numbers or Identifiers) and is related to CWE-338 (Use of Cryptographically Weak Pseudo-Random Number Generator). No known exploits are currently reported in the wild, and no official patches or mitigations have been published as of the vulnerability disclosure date (September 20, 2025).

For European organizations using BLUEFEET Starch versions 0.14 or earlier, this vulnerability poses a significant risk to session confidentiality and integrity. Attackers who can predict session IDs may hijack active sessions, impersonate legitimate users, and gain unauthorized access to sensitive data or systems. This can lead to data breaches, unauthorized transactions, and potential lateral movement within networks. The impact is particularly critical for web applications handling personal data protected under GDPR, as unauthorized access could result in regulatory penalties and reputational damage. Additionally, sectors such as finance, healthcare, and government, which often rely on session-based authentication, may face operational disruptions and loss of trust. Since the vulnerability exploits weak session ID generation, it can be leveraged remotely without requiring user interaction, increasing the attack surface. The absence of known exploits suggests limited current active threat but also indicates the need for proactive mitigation to prevent future exploitation.

European organizations should immediately audit their use of BLUEFEET Starch to identify affected versions. Until an official patch is released, organizations should implement compensating controls such as: 1) Replacing the default session ID generator with a cryptographically secure random number generator (e.g., using Perl modules like Crypt::Random or system-level secure RNGs). 2) Implementing additional session management controls, including strict session expiration, IP address binding, and multi-factor authentication to reduce the risk of session hijacking. 3) Monitoring web server logs for suspicious session ID patterns or repeated failed access attempts that may indicate guessing attacks. 4) Ensuring HTTP headers do not leak epoch time or other predictable values that could aid attackers. 5) Planning for an upgrade to a patched version of Starch once available or considering alternative software with secure session management. 6) Educating developers and administrators on secure session management best practices to prevent similar vulnerabilities.