GoFiber Vulnerable to X-Real-IP Spoofing via Header.Add() in BalancerForward

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS

• CVE-2026-45045: 0.46% estimated exploitation activity in the next 30 days; percentile 40.16 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The BalancerForward proxy helper in GoFiber uses Header.Add() instead of Header.Set() when injecting the X-Real-IP header. This appends the real client IP as a second header value rather than replacing any attacker-supplied value. Upstream servers that read the first X-Real-IP header (nginx, Express, most HTTP servers) use the attacker's spoofed IP for logging, rate limiting, and access control. Vulnerable Code File: middleware/proxy/proxy.go, lines 270-285 Data Flow 1. Attacker sends request with X-Real-IP: 10.0.0.1 (spoofed internal IP) 2. BalancerForward handler executes at line 282 3. c.Request().Header.Add("X-Real-IP", c.IP()) APPENDS the real IP as a second header 4. Upstream server receives: X-Real-IP: 10.0.0.1 AND X-Real-IP: <real-attacker-ip 5. Most HTTP servers (nginx, Node.js, Apache) read the FIRST value 6. Upstream uses 10.0.0.1 for all IP-dependent logic Impact - Rate limit bypass: IP-based rate limiting at the upstream uses the spoofed IP, allowing unlimited…

Published by the source

2 Jul 2026, 13:50 UTC

Last modified by the source

4 Aug 2026, 21:52 UTC

Source last checked

26 Oct 2026, 15:28 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-gcfq-8gqf-4876

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# Patch Next advisory brief: CVE-2026-45045

Advisory: GoFiber Vulnerable to X-Real-IP Spoofing via Header.Add() in BalancerForward
IDs: CVE-2026-45045, GHSA-gcfq-8gqf-4876
Record: https://patchnext.com/advisories/cve-2026-45045 (revision 1, source checked 26 Oct 2026, 15:28 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/gofiber/fiber/v3 3.3.0; github.com/gofiber/fiber/v2 2.52.14. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/gofiber/fiber/v3: affected <= 3.2.0; fixed in 3.3.0
- Go github.com/gofiber/fiber/v2: affected <= 2.52.13; fixed in 2.52.14

## Suggested inspection (read-only)
- Go github.com/gofiber/fiber/v3: check the installed version with your package manager.
- Go github.com/gofiber/fiber/v2: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/gofiber/fiber/v3, github.com/gofiber/fiber/v2.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-gcfq-8gqf-4876 (GitHub-reviewed advisory GHSA-gcfq-8gqf-4876 lists affected ranges: Go github.com/gofiber/fiber/v3 >=0 =0 <=2.52.13)

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