Fiber v2 on Go has a UUID bug This article explores uuid bug fiber. . Fiber v2, a well-known Go web framework, has a serious flaw that could let hackers take over user sessions, get past security measures, and disrupt services.

The framework maintainer discovered the bug six days ago, and it impacts all Fiber v2 versions running on Go 1.23 or earlier. The UUID generation functions of Fiber v2, which are utilized throughout the framework to generate session unique identifiers, CSRF tokens, and other security-critical components, are the source of the vulnerability. These functions silently revert to producing a predictable "zero UUID" (00000000-0000-0000-0000-000000000000) in the rare but possible event that the system's random number generator is unable to provide secure randomness, rather than warning developers of the issue.

Because developers are unable to determine whether their security tokens have become predictable, this silent failure is especially risky. Details of the Attribute CVE ID: CVE-2025-66630 (AV:N/AC:H/PR:N/UI:N) CVSS v4.0 9.2 Weak PRNG, CWE CWE-338 Versions Affected < 2.52.11 (Go 1.23 or earlier) Effects Reliable UUID fallback to zero UUID The problem mostly impacts users who are running Use versions prior to 1.24 because more recent versions react differently to random failures, either blocking or panicking instead of returning errors. Actual Attack Situations There are several security risks due to the predictable UUID generation.

Attackers could pose as authentic users without stealing credentials because they could anticipate session identifiers. CSRF protection mechanisms that rely on these UUIDs become ineffective, leaving cross-site request forgery attacks unimpeded. Authentication tokens become guessable, potentially granting unauthorized access to protected resources.

The denial-of-service risk is arguably the most worrisome since it can lead to data overwrites and system instability when several users receive the same zero UUID because session stores and rate limiters collapse into a single shared key. Although random failures are uncommon in modern Linux systems, they are more likely to occur in specific environments. More vulnerable are embedded devices, sandboxed processes, containerized apps, and misconfigured systems with improper access to randomness sources (/dev/urandom).

The vulnerability may also be triggered by systems with limited security policies and sandboxed environments. Fiber version 2.52.11 has been released to address the critical vulnerability, per the published security advisory. Fiber v2 users should update to this patched version right away.

The fix, which has been given the CVE-2025-66630 assignment, has a CVSS score of 8.7 out of 10 and is classified as "Critical." Additionally, system administrators should confirm that secure randomness sources are properly accessible in their environments. X for daily cybersecurity updates, LinkedIn, and logs for any unusual patterns of identical session identifiers that could point to exploitation attempts.

To have your stories featured, get in touch with us.