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

What is CVE-2026-45045?

CVE-2026-45045 is a medium-severity vulnerability in gofiber fiber, published on 8 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official 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.

Weakness: CWE-290

Which versions are affected by CVE-2026-45045?

5 open source packages ship an affected version, including github.com/gofiber/fiber/v3 and github.com/gofiber/fiber/v2. It affects 1 product.

Products include Gofiber Fiber.

How do I fix CVE-2026-45045?

Upgrade github.com/gofiber/fiber/v3 to 3.3.0 or later.

Is CVE-2026-45045 being exploited?

There is no known exploitation of CVE-2026-45045 in the wild and no public exploit code.

Other vulnerabilities in gofiber fiber

• CVE-2024-38513 Fiber Session Middleware Token Injection Vulnerability Critical 10.0
• CVE-2023-45128 CSRF Token Reuse Vulnerability in fiber Critical 10.0
• CVE-2024-25124 Fiber has Insecure CORS Configuration, Allowing Wildcard Origin with Credentials Critical 9.4
• CVE-2025-66630 Fiber insecurely fallsback in utils.UUIDv4() / utils.UUID() — predictable / zero‑UUID on crypto/rand failure Critical 9.2
• CVE-2025-54801 Fiber Susceptible to Crash via `BodyParser` Due to Unvalidated Large Slice Index in Decoder High 8.7

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-gcfq-8gqf-4876, GO-2026-5887, MINI-5g7v-9g4p-6349, MINI-6r5m-9fvh-3mx8, MINI-7w8h-jr24-h956, MINI-8vvp-fqcg-3cqh and 1 more.