Medium severity · published Jul 8, 2026
CVE-2026-45045
Fiber: X-Real-IP Spoofing via Header.Add() in BalancerForward
5.3
CVSS
0.5%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
Low
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 40% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FI
fiber · gofiber
>= 3.0.0-beta.2, < 3.3.0; < 2.52.14 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-45045
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-45045
Patch
https://github.com/gofiber/fiber/commit/1403cc8292da3220e9316960b4030cc722a0f396
Patch
https://github.com/gofiber/fiber/commit/33c9501288ab47a429c8b5e701493f0c3c0af37d
Issue Tracking
https://github.com/gofiber/fiber/pull/4260
Issue Tracking
https://github.com/gofiber/fiber/pull/4495
Release Notes
https://github.com/gofiber/fiber/releases/tag/v2.52.14
Release Notes
https://github.com/gofiber/fiber/releases/tag/v3.3.0
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