CVE-2026-44332
MediumCVSS 5.3Exploitation Probability (EPSS)
Low risk40th percentile - higher than 40% of all known CVEs
Summary
In the Fiber web framework for Go prior to version 3.3.0, the default Authorizer function in the BasicAuth middleware uses short-circuit evaluation that skips password hash comparison for non-existent usernames. This allows reliable remote username enumeration through response timing differences.
Risk Assessment
An attacker can remotely and stealthily determine which usernames are registered in the system, facilitating targeted brute-force or social engineering attacks.
Recommendation
Immediately upgrade the Fiber library to version 3.3.0 or later, which includes a fix that prevents username enumeration.
Other vulnerabilities in Fiber
See all- CVE-2026-53624Medium
In the Fiber web framework for Go prior to version 3.4.0, the helmet middleware incorrectly checks the protocol using c.Protocol() instead of c.Scheme(), causing the Strict-Transport-Security header to never be set even when HSTSMaxAge is configured. This issue is fixed in version 3.4.0.
- CVE-2026-45045Medium
In the Fiber web framework for Go, prior to versions 3.3.0 and 2.52.14, the BalancerForward proxy helper in middleware/proxy/proxy.go uses Header.Add() instead of Header.Set() when injecting the X-Real-IP header. This allows an attacker to supply a first X-Real-IP value that gets forwarded to upstream servers for logging, rate limiting, and access control.
Original NVD description (English source)
Fiber is an Express inspired web framework written in Go. Prior to 3.3.0, the default Authorizer function in the BasicAuth middleware in middleware/basicauth/config.go uses short-circuit evaluation that skips password hash comparison for non-existent usernames, enabling reliable remote username enumeration through response timing differences. This issue is fixed in version 3.3.0.