What’s Vulnerable › Vulnerabilities

CVE-2026-45045: Fiber: X-Real-IP Spoofing via Header.Add() in BalancerForward

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-07-08 · updated 2026-10-25
• Weakness: CWE-290

Description

Fiber is an Express inspired web framework written in Go. Prior to 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 X-Real-IP, allowing an attacker-supplied first X-Real-IP value to be forwarded to upstream servers for logging, rate limiting, and access control. This issue is fixed in version 3.3.0 and 2.52.14.

Affected products

• gofiber fiber: before 2.52.14; from 3.0.0 before 3.3.0 — fixed in 2.52.14, 3.3.0

How to fix

Upgrade to a fixed version: gofiber fiber 2.52.14, 3.3.0. Check the vendor advisory for mitigations.

References

• https://github.com/gofiber/fiber/commit/1403cc8292da3220e9316960b4030cc722a0f396
• https://github.com/gofiber/fiber/commit/33c9501288ab47a429c8b5e701493f0c3c0af37d
• https://github.com/gofiber/fiber/pull/4260
• https://github.com/gofiber/fiber/pull/4495
• https://github.com/gofiber/fiber/releases/tag/v2.52.14
• https://github.com/gofiber/fiber/releases/tag/v3.3.0
• https://github.com/gofiber/fiber/security/advisories/GHSA-gcfq-8gqf-4876

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