CVE-2025-66630: The Null Identity: Unmasking Fiber's Critical 'Zero-UUID' Vulnerability

The Null Identity: Unmasking Fiber's Critical 'Zero-UUID' Vulnerability

Vulnerability ID: CVE-2025-66630
CVSS Score: 9.2
Published: 2026-02-09

A critical failure in the Fiber web framework's random number generation logic allows for the creation of predictable, zero-value UUIDs. This flaw leads to catastrophic session hijacking and CSRF bypass scenarios when the underlying system entropy source is exhausted or unavailable.

TL;DR

Fiber < 2.52.11 silently ignores RNG failures, defaulting to an all-zero UUID. Attackers can exploit this to predict session IDs, hijack user accounts, and bypass security middleware.

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⚠️ Exploit Status: POC

Technical Details

• CWE ID: CWE-338
• Attack Vector: Network
• CVSS Score: 9.2 (Critical)
• Impact: Session Hijacking, CSRF Bypass
• Exploit Status: PoC Available
• Patch Date: 2026-02-09

Affected Systems

• Fiber Web Framework (Go)
• Applications using Fiber Session Middleware
• Applications using Fiber CSRF Middleware
• Applications using Fiber RequestID Middleware
• github.com/gofiber/fiber/v2: < 2.52.11 (Fixed in: 2.52.11)

Code Analysis

Commit: eb874b6

Fix: panic on UUID generation failure

func UUID() string {
-   if _, err := rand.Read(uuidSeed[:]); err != nil {
-       return
-   }
+   if _, err := rand.Read(uuidSeed[:]); err != nil {
+       panic(fmt.Sprintf("utils: failed to seed UUID generator: %v", err))
+   }
}

Exploit Details

• Theoretical: Environment-based exploitation via entropy starvation or file descriptor exhaustion.

Mitigation Strategies

• Update Fiber framework immediately.
• Upgrade Go runtime to 1.24+ for better entropy handling.
• Monitor system entropy and file descriptor usage.

Remediation Steps:

1. Run go get -u github.com/gofiber/fiber/v2 to fetch v2.52.11.
2. Rebuild the application binary.
3. Audit logs for any past occurrences of session ID 00000000-0000-0000-0000-000000000000.

References

• GitHub Security Advisory
• NVD Entry

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Read the full report for CVE-2025-66630 on our website for more details including interactive diagrams and full exploit analysis.