CVE-2026-25891
📋 TL;DR
A path traversal vulnerability in Fiber's static middleware on Windows allows remote attackers to bypass sanitization and read arbitrary files from the server filesystem. This affects Fiber v3 through version 3.0.0 when serving static files on Windows systems.
💻 Affected Systems
- Fiber (Go web framework)
📦 What is this software?
Fiber by Gofiber
⚠️ Risk & Real-World Impact
Worst Case
Complete server filesystem compromise including sensitive configuration files, credentials, and application source code disclosure.
Likely Case
Unauthorized access to sensitive files like configuration files, environment variables, or application data.
If Mitigated
Limited file access restricted by OS permissions and proper network segmentation.
🎯 Exploit Status
Simple path traversal payloads can bypass the static middleware sanitizer on Windows.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v3.1.0
Vendor Advisory: https://github.com/gofiber/fiber/security/advisories/GHSA-m3c2-496v-cw3v
Restart Required: Yes
Instructions:
1. Update Fiber dependency to v3.1.0 or later. 2. Run 'go get github.com/gofiber/fiber/v3@v3.1.0'. 3. Rebuild and redeploy your application. 4. Restart the application server.
🔧 Temporary Workarounds
Disable static middleware on Windows
windowsTemporarily disable or remove static file serving middleware until patching is possible.
// Remove or comment out app.Static() calls in your Fiber application
Use reverse proxy for static files
allServe static files through a separate web server (nginx, Apache) instead of Fiber's static middleware.
🧯 If You Can't Patch
- Implement strict network access controls to limit exposure of vulnerable endpoints
- Deploy web application firewall (WAF) with path traversal protection rules
🔍 How to Verify
Check if Vulnerable:
Check if using Fiber v3.0.0 or earlier on Windows with static middleware enabled.Check Version:
go list -m github.com/gofiber/fiber/v3Verify Fix Applied:
Verify Fiber version is v3.1.0 or later and test path traversal attempts return 404/403 instead of file contents.📡 Detection & Monitoring
Log Indicators:
- Unusual file access patterns in application logs
- Multiple 404/403 errors for path traversal attempts
Network Indicators:
- HTTP requests containing '../' or '..\' patterns in URLs
SIEM Query:
web.url:*..* AND (web.url:*../* OR web.url:*..\*)