{"id":"CVE-2026-45045","aliases":["GHSA-gcfq-8gqf-4876","GO-2026-5887"],"url":"https://o3.security/vulnerability/CVE-2026-45045","summary":"Fiber: X-Real-IP Spoofing via Header.Add() in BalancerForward","details":"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.","published":"2026-07-08T19:26:26.580Z","modified":"2026-08-27T18:26:05.522202588Z","cvss":{"score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"},"epss":{"score":0.00463,"percentile":0.38564,"asOf":"2026-09-07"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/gofiber/fiber/v3","fixedVersion":"3.3.0"},{"ecosystem":"Go","name":"github.com/gofiber/fiber/v2","fixedVersion":"2.52.14"}],"fix":{"url":"https://github.com/gofiber/fiber/commit/1403cc8292da3220e9316960b4030cc722a0f396","label":"gofiber/fiber@1403cc8"},"references":[{"type":"WEB","url":"https://github.com/gofiber/fiber/releases/tag/v2.52.14"},{"type":"WEB","url":"https://github.com/gofiber/fiber/releases/tag/v3.3.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45045.json"},{"type":"ADVISORY","url":"https://github.com/gofiber/fiber/security/advisories/GHSA-gcfq-8gqf-4876"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-45045"},{"type":"FIX","url":"https://github.com/gofiber/fiber/commit/1403cc8292da3220e9316960b4030cc722a0f396"},{"type":"FIX","url":"https://github.com/gofiber/fiber/commit/33c9501288ab47a429c8b5e701493f0c3c0af37d"},{"type":"FIX","url":"https://github.com/gofiber/fiber/pull/4260"},{"type":"FIX","url":"https://github.com/gofiber/fiber/pull/4495"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-27T18:26:05.522202588Z"}}