---
title: "CVE-2025-66630: Fiber has an insecure fallback in utils.UUIDv4() / utils.UUID() — predictable / zero‑UUID on crypto/rand failure"
url: https://erroneo.us/security/cve/CVE-2025-66630/
description: "CVE-2025-66630 (github.com/gofiber/fiber/v2 (Go)): Fiber is an Express inspired web framework written in Go. Before 2.52.11, on Go versions prior to 1.24…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-02-09
date_modified: 2026-02-10
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2025-66630"
kev: false
cvss: 9.2
epss: 0.00535
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2025-66630: Fiber has an insecure fallback in utils.UUIDv4() / utils.UUID() — predictable / zero‑UUID on crypto/rand failure

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.5% , percentile 44: FIRST’s model estimates a 0.5% chance of exploitation activity in the next 30 days, higher than 44% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes github.com/gofiber/fiber/v2 (Go) < 2.52.11, fixed in 2.52.11 . Check your lockfile, including transitive dependencies.

## What it is

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 packages

- Go `github.com/gofiber/fiber/v2` < 2.52.11 → fixed: 2.52.11

## Affected products (CVE record)

- gofiber fiber: < 2.52.11

## Severity

- GitHub_M CVSS 4.0: 9.2 `CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N`
- GitHub CVSS 4.0: 9.2 `CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable no , technical impact partial .
- FIRST EPSS (model of 2026-10-21): 0.53% probability of exploitation activity in the next 30 days; percentile 44.

## Sources

- [GitHub Advisory GHSA-68rr-p4fp-j59v](https://github.com/advisories/GHSA-68rr-p4fp-j59v)
- [CVE.org record CVE-2025-66630](https://www.cve.org/CVERecord?id=CVE-2025-66630)
- [NVD entry CVE-2025-66630](https://nvd.nist.gov/vuln/detail/CVE-2025-66630)
- [github.com](https://github.com/gofiber/fiber/security/advisories/GHSA-68rr-p4fp-j59v)
- [github.com](https://github.com/gofiber/fiber/commit/eb874b6f6c5896b968d9b0ab2b56ac7052cb0ee1)
- [github.com](https://github.com/gofiber/fiber/releases/tag/v2.52.11)

---
Source page: https://erroneo.us/security/cve/CVE-2025-66630/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt