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.
{
"cna_assigner": "GitHub_M",
"cwe_ids": [
"CWE-290"
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45045.json"
}{
"source": [
"AFFECTED_FIELD",
"REFERENCES"
],
"extracted_events": [
{
"introduced": "3.0.0-beta.2"
},
{
"fixed": "3.3.0"
},
{
"introduced": "0"
},
{
"fixed": "2.52.14"
}
]
}