What’s Vulnerable › Vulnerabilities

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

• Severity: critical (CVSS 9.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-02-09 · updated 2026-06-17
• Weakness: CWE-338

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.

Affected products

• gofiber fiber: before 2.52.11 — fixed in 2.52.11

How to fix

Upgrade to a fixed version: gofiber fiber 2.52.11. Check the vendor advisory for mitigations.

References

• https://github.com/gofiber/fiber/commit/eb874b6f6c5896b968d9b0ab2b56ac7052cb0ee1
• https://github.com/gofiber/fiber/releases/tag/v2.52.11
• https://github.com/gofiber/fiber/security/advisories/GHSA-68rr-p4fp-j59v

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