CVE-2025-66565 CRITICAL

CVE-2025-66565: Fiber Utils UUIDv4 and UUID Silent Fallback to Predictable Values

Vendor Gofiber
Product utils
Weakness CWE-252
Published December 9, 2025
Last update December 9, 2025

CVSS base score

9.3/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality
Integrity

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

December 9, 2025 CVE published
December 9, 2025 Record updated