CVE-2025-48075: Gofiber Fiber DOS Vulnerability

CVE-2025-48075 Overview

CVE-2025-48075 is a Denial of Service vulnerability affecting the GoFiber web framework, an Express-inspired web framework written in Go. The vulnerability exists in the fiber.Ctx.BodyParser function which can map flat data to nested slices using key[idx]value syntax. When a negative index value is provided by a user, the function triggers a panic instead of returning an error, leading to application crashes.

Critical Impact

Unauthenticated remote attackers can crash Fiber-based web applications by sending malformed HTTP requests with negative array indices, resulting in denial of service.

Affected Products

• GoFiber Fiber versions 2.52.6 and prior to 2.52.7
• Applications using fiber.Ctx.BodyParser for request body parsing
• Go web services built on vulnerable Fiber framework versions

Discovery Timeline

• 2025-05-22 - CVE-2025-48075 published to NVD
• 2025-05-30 - Last updated in NVD database

Technical Details for CVE-2025-48075

Vulnerability Analysis

This vulnerability is classified under CWE-129 (Improper Validation of Array Index). The core issue lies in insufficient input validation within the fiber.Ctx.BodyParser function when processing user-supplied array indices in form data. The function supports a syntax where developers can map flat form data to nested Go slices using bracket notation (e.g., items[0]=value). However, the implementation fails to validate that the provided index value is non-negative before attempting to use it for slice access.

When a negative index is supplied (e.g., items[-1]=malicious), Go's runtime panics due to the invalid slice access, crashing the entire application. Since HTTP request body data is directly controlled by users, any attacker with network access to the application can trivially trigger this condition.

Root Cause

The root cause is improper validation of array indices in the request body parsing logic. The BodyParser function does not check if array index values extracted from request keys are negative integers before using them to access or resize Go slices. In Go, accessing a slice with a negative index causes a runtime panic that, if unrecovered, terminates the goroutine or entire application.

Attack Vector

The attack is network-based and requires no authentication or special privileges. An attacker can craft an HTTP POST request containing form data with negative array indices in the key names. When the target application uses fiber.Ctx.BodyParser to parse the request body into a struct with slice fields, the malicious negative index triggers a panic.

The vulnerability can be exploited by sending a request containing body content such as:

POST /endpoint HTTP/1.1
Content-Type: application/x-www-form-urlencoded

items[-1]=malicious_value

When the server attempts to parse this into a struct with an Items []string field, the negative index causes the panic. This attack is trivial to execute and requires no special tools or authentication.

Detection Methods for CVE-2025-48075

Indicators of Compromise

• Unexpected application crashes or restarts in Fiber-based services
• HTTP 500 errors or connection resets following POST/PUT requests
• Panic stack traces in application logs referencing fiber.Ctx.BodyParser
• Runtime panic messages indicating invalid slice index access

Detection Strategies

• Monitor application logs for Go runtime panic messages with stack traces pointing to body parsing functions
• Implement request logging to capture HTTP requests with bracket notation containing negative numbers in form data keys
• Deploy Web Application Firewall (WAF) rules to detect and block requests with patterns like [key[- or \[\-[0-9]+\] in request bodies
• Set up crash monitoring and alerting for Fiber application processes

Monitoring Recommendations

• Configure application process monitoring to detect unexpected restarts or crashes
• Enable detailed request logging for all endpoints using BodyParser functionality
• Set up real-time alerting for patterns matching negative array index exploitation attempts
• Monitor service availability metrics to detect potential DoS attack patterns

How to Mitigate CVE-2025-48075

Immediate Actions Required

• Upgrade GoFiber Fiber to version 2.52.7 or later immediately
• Review all code paths that use fiber.Ctx.BodyParser for potential exposure
• Implement input validation middleware to reject requests with negative array indices
• Consider adding recovery middleware to catch panics and prevent complete application crashes

Patch Information

GoFiber has released version 2.52.7 which fixes this vulnerability by properly validating array indices before use. The fix ensures that negative indices return an appropriate error instead of causing a panic.

For detailed patch information, see the GitHub commit e115c08b8f059a4a031b492aa9eef0712411853d and the GitHub Security Advisory GHSA-hg3g-gphw-5hhm.

Workarounds

• Implement custom middleware to validate and sanitize array indices in request bodies before they reach BodyParser
• Add a recovery middleware using fiber.Config{Recover: true} to prevent panics from crashing the entire application
• Use input validation to reject any form keys containing bracket notation with negative numbers
• Deploy a reverse proxy or WAF to filter malicious requests before they reach the application

# Update GoFiber to patched version
go get github.com/gofiber/fiber/v2@v2.52.7

# Verify the updated version
go list -m github.com/gofiber/fiber/v2