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Vulnerability · Published Jul 8, 2026 · Assigned by GitHub_M

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

Medium 5.3

In plain English

A medium-severity authentication bypass by spoofing in fiber from gofiber. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 40% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)5.3Medium
Exploit odds (30 days)0.5%top 59.7% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Gogithub.com/gofiber/fiber/v22.52.14GHSA-gcfq-8gqf-4876
Gogithub.com/gofiber/fiber/v33.3.0GHSA-gcfq-8gqf-4876
Gogithub.com/gofiber/fiber/v33.3.0GO-2026-5887
Ubuntu:26.10golang-github-gofiber-fiberno fix listedUBUNTU-CVE-2026-45045
Ubuntu:26.10golang-github-gofiber-fiber-v2no fix listedUBUNTU-CVE-2026-45045

Affected products (as reported)

VendorProductVersions
gofiber fiber >= 3.0.0-beta.2, < 3.3.0< 2.52.14

Weakness: CWE-290 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

References