CVE-2025-66630: Fiber insecurely fallsback in utils.UUIDv4() / utils.UUID() — predictable / zero‑UUID on crypto/rand failure

Vulnerability summary

CVE-2025-66630 is a critical (CVSS 9.4) vulnerability in gofiber fiber. EPSS estimates a 0.53% chance of exploitation in the next 30 days, higher than 44.3% of scored vulnerabilities.

Timeline

1. 09-02-2026
   PublishedVulnerability first disclosed.
2. 10-02-2026
   Last modifiedVulnerability information updated.

Description

Fiber is an Express inspired web framework written in Go. Before 2.52.11, on Go versions prior to 1.24, the underlying crypto/rand implementation can return an error if secure randomness cannot be obtained. Because no error is returned by the Fiber v2 UUID functions, application code may unknowingly rely on predictable, repeated, or low-entropy identifiers in security-critical pathways. This is especially impactful because many Fiber v2 middleware components (session middleware, CSRF, rate limiting, request-ID generation, etc.) default to using utils.UUIDv4(). This vulnerability is fixed in 2.52.11.

• CWE-338Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)The product uses a Pseudo-Random Number Generator (PRNG) in a security context, but the PRNG's algorithm is not cryptographically strong.