CVE-2020-15111: CRLF vulnerability in github.com/gofiber/fiber

Background

The package under scrutiny is github.com/gofiber/fiber, which is a Go package that provides a lightweight web framework for building fast and efficient web applications. It offers various features such as routing, middleware support, and request/response handling. The vulnerability in this package allows for a CRLF (Carriage Return Line Feed) attack, where a maliciously crafted filename can lead to the download of a file with an attacker-controlled filename and the injection of additional headers into an HTTP response.

Vulnerability Detail

The CRLF vulnerability in github.com/gofiber/fiber arises due to improper input sanitization. An attacker can exploit this vulnerability by manipulating the filename parameter in a file download request. By injecting special characters such as carriage return and line feed, the attacker can control the filename and introduce additional headers into the HTTP response. This can lead to various security risks, including the potential for content spoofing, HTTP response splitting, and cross-site scripting (XSS) attacks.

go get github.com/gofiber/fiber@v1.14.6

go get github.com/gofiber/fiber@v1.12.6

Workaround

If updating the package is not immediately feasible, a temporary workaround can be implemented by manually sanitizing the filename parameter before processing it. This can involve removing or encoding any special characters that could be used for CRLF injection. Here is an example of how the filename parameter can be sanitized using Go code:

import (
	"net/http"
	"strings"
)

func downloadFile(w http.ResponseWriter, r *http.Request) {
	filename := sanitizeFilename(r.URL.Query().Get("filename"))
	// Rest of the code for file download
}

func sanitizeFilename(filename string) string {
	filename = strings.ReplaceAll(filename, "\r", "")
	filename = strings.ReplaceAll(filename, "\n", "")
	// Additional sanitization logic if required
	return filename
}

Conclusion

The CRLF vulnerability in github.com/gofiber/fiber can be exploited by manipulating the filename parameter in a file download request. It is crucial to update the package to version 1.12.6 or later to fix this vulnerability. If immediate update is not possible, manual sanitization of the filename parameter can serve as a temporary workaround. Regularly monitoring and updating dependencies, as well as following secure coding practices, are essential for maintaining the security of web applications. For further support on vulnerability remediation, you can reach out to DevNack.com.

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