CVE-2026-45045 (CVSS 5.3)

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.

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CVSS v3.1 Score

5.3

MEDIUM

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

EPSS — Exploit Prediction

0.0046

Probability of exploitation

0.37%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-290 CWE-290

References

Other 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

Frequently Asked Questions

What is CVE-2026-45045? +

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. It has a CVSS v3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2026-45045? +

CVE-2026-45045 has a CVSS v3.1 score of 5.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0046, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-45045? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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