CVE-2025-66630 is a vulnerability in the GoFiber web framework, specifically versions prior to 2.52.11, where the UUID generation relies on the Go crypto/rand package for secure random number generation. On Go versions before 1.24, the crypto/rand implementation can fail to provide secure randomness and return an error. However, Fiber’s UUID functions do not propagate this error, resulting in the generation of UUIDs with predictable, repeated, or low entropy values. This weakness is critical because many Fiber v2 middleware components—such as session middleware, CSRF protection, rate limiting, and request ID generation—default to using the vulnerable utils.UUIDv4() function. Consequently, security-critical identifiers may be guessable or reused, undermining confidentiality and integrity protections. The vulnerability is classified under CWE-338 (Use of Cryptographically Weak PRNG). The CVSS 4.0 vector indicates network attack vector, high attack complexity, no privileges or user interaction required, and high impact on confidentiality and integrity, with low impact on availability. No known exploits are currently reported in the wild. The issue is resolved by upgrading Fiber to version 2.52.11 or later, which properly handles errors from crypto/rand and ensures secure UUID generation. Additionally, using Go runtime 1.24 or newer is necessary to avoid the underlying crypto/rand issue. Organizations relying on Fiber middleware for security-critical functions should prioritize patching to prevent potential exploitation that could lead to session hijacking, CSRF bypass, or abuse of rate limiting controls.

For European organizations, this vulnerability poses a significant risk to web applications built on the GoFiber framework, especially those using versions prior to 2.52.11 on Go runtimes older than 1.24. The predictable or low-entropy UUIDs can allow attackers to guess session identifiers, CSRF tokens, or request IDs, leading to unauthorized access, session hijacking, or bypass of security controls. This undermines confidentiality and integrity of user sessions and application data. Organizations in sectors such as finance, healthcare, government, and critical infrastructure that rely on Fiber for web services could face data breaches, fraud, or service disruption. The vulnerability’s network attack vector and lack of required authentication mean attackers can exploit it remotely without user interaction, increasing the threat surface. Given the widespread use of Go in modern web development and Fiber’s popularity for high-performance web applications, the impact could be broad, affecting both public-facing services and internal applications. Failure to patch could also lead to compliance violations under GDPR and other data protection regulations due to compromised data security.

1. Upgrade the GoFiber framework to version 2.52.11 or later immediately to ensure the UUID generation properly handles errors from the crypto/rand package and produces secure random values. 2. Upgrade the Go runtime environment to version 1.24 or newer, as earlier versions have known issues with crypto/rand that contribute to this vulnerability. 3. Conduct a thorough code review of all security-critical components that rely on UUIDs or random identifiers, verifying that no silent failures or fallback to weak randomness exist. 4. Implement additional monitoring and anomaly detection for session reuse, CSRF token reuse, or unusual request patterns that might indicate exploitation attempts. 5. Where possible, replace default Fiber middleware UUID generation with custom implementations that explicitly check for randomness errors and enforce entropy requirements. 6. Educate development and security teams about the risks of silent failures in cryptographic functions and the importance of error handling in security-sensitive code. 7. For legacy systems that cannot be immediately upgraded, consider compensating controls such as additional authentication layers or token rotation to reduce risk exposure.