CVE-2025-66565
Fix: gofiber/utils@6c6cf04CVE-2025-66565 is a CWE-252 vulnerability in github.com/gofiber/utils/v2. O3 Security confirms whether CVE-2025-66565 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Fiber Utils UUIDv4 and UUID Silent Fallback to Predictable Values
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2025-66565.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
github.com/gofiber/utils/v2🐹github.com/gofiber/utilsReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Fiber Utils is a collection of common functions created for Fiber. In versions 2.0.0-rc.3 and below, when the system's cryptographic random number generator (crypto/rand) fails, both functions silently fall back to returning predictable UUID values, including the zero UUID "00000000-0000-0000-0000-000000000000". The vulnerability occurs through two related but distinct failure paths, both ultimately caused by crypto/rand.Read() failures, compromising the security of all Fiber applications using these functions for security-critical operations. This issue is fixed in version 2.0.0-rc.4.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/gofiber/utils/v2 | all versions | 2.0.0-rc.4 |
| 🐹Go | github.com/gofiber/utils | all versions | 1.2.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/gofiber/utils/v2. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/gofiber/utils/v2 to 2.0.0-rc.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-66565 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2025-66565 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2025-66565. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2025-66565 in your dependencies?
O3 detects CVE-2025-66565 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.