V3: CWE-290: Authentication Bypass by Spoofing in gofiber fiber (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.
AI Analysis
Technical Summary
In the GoFiber framework (github.com/gofiber/fiber/v3), the BalancerForward proxy helper incorrectly uses the HTTP Header.Add() method instead of Header.Set() when forwarding the X-Real-IP header. This causes the real client IP to be appended rather than replacing any existing X-Real-IP header. Since many upstream servers read the first X-Real-IP header, an attacker can supply a spoofed X-Real-IP header that is trusted over the appended real IP. This vulnerability affects versions <3.3.0 and <=2.52.13.
Potential Impact
This vulnerability allows an attacker to spoof the X-Real-IP header value seen by upstream servers, potentially bypassing IP-based access controls or logging accurate client IP addresses. The integrity of client IP information is compromised, which can affect security policies relying on correct IP identification. There is no direct confidentiality or availability impact reported.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, users should consider implementing additional validation or filtering of the X-Real-IP header at the application or proxy level to prevent spoofing. Monitor vendor channels for updates regarding an official fix.
V3: CWE-290: Authentication Bypass by Spoofing in gofiber fiber (CVE-2026-45045)
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 v3.1
Score 5.3medium
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
In the GoFiber framework (github.com/gofiber/fiber/v3), the BalancerForward proxy helper incorrectly uses the HTTP Header.Add() method instead of Header.Set() when forwarding the X-Real-IP header. This causes the real client IP to be appended rather than replacing any existing X-Real-IP header. Since many upstream servers read the first X-Real-IP header, an attacker can supply a spoofed X-Real-IP header that is trusted over the appended real IP. This vulnerability affects versions <3.3.0 and <=2.52.13.
Potential Impact
This vulnerability allows an attacker to spoof the X-Real-IP header value seen by upstream servers, potentially bypassing IP-based access controls or logging accurate client IP addresses. The integrity of client IP information is compromised, which can affect security policies relying on correct IP identification. There is no direct confidentiality or availability impact reported.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, users should consider implementing additional validation or filtering of the X-Real-IP header at the application or proxy level to prevent spoofing. Monitor vendor channels for updates regarding an official fix.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-gcfq-8gqf-4876
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-45045"]
- Ecosystems
- ["Go"]
- Database Specific Severity
- MODERATE
- Cvss Version
- 3.1
Threat ID: 6a46ece327e9c79719440e5f
Added to database: 07/02/2026, 22:57:39 UTC
Last enriched: 07/10/2026, 07:52:57 UTC
Last updated: 07/31/2026, 19:22:59 UTC
Views: 88
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