Fiber · Fiber · CVE-2026-45045
**Name of the Vulnerable Software and Affected Versions**
Fiber versions prior to 3.3.0
Fiber versions prior to 2.52.14
**Description**
The `BalancerForward` proxy helper in `middleware/proxy/proxy.go` uses the `Header.Add()` function instead of `Header.Set()` when injecting the `X-Real-IP` header. This behavior appends the real client IP as a second value rather than replacing any existing value provided by a user. Consequently, upstream servers that read only the first `X-Real-IP` header may use an attacker-supplied spoofed IP for logging, rate limiting, and access control, potentially leading to IP ACL bypass, rate limit bypass, audit log poisoning, and geolocation bypass.
**Recommendations**
Update Fiber to version 3.3.0 or later.
Update Fiber to version 2.52.14 or later.