CVE-2023-42117 - Exim Improper Neutralization of Special Elements Remote Code Execution Vulnerability: A Deep Dive into Exploit Details, Code Snippets, and References

Exim servers have become a target of remote code execution attacks, and the CVE-2023-42117 discloses a vulnerability specifically affecting these installations. This critical flaw allows remote attackers to execute arbitrary code on the targeted systems without the need for authentication. This blog post will delve into the nitty-gritty details of this vulnerability, including code snippets and references that demonstrate how the attacker can exploit this weakness.

Exploit Details

The vulnerability in question resides in the smtp service provided by Exim, which listens on TCP port 25 by default. It originates from the improper validation of user-supplied data, leading to memory corruption and enabling remote code execution.

The attacker can exploit this weakness by crafting malicious payloads and injecting them into the smtp service. By doing so, they can execute code in the context of the currently running process, thus gaining control over the affected installation.

Below is a sample code snippet showing how an attacker might leverage this vulnerability

import socket

target_host = "TARGET_IP_ADDRESS"
target_port = 25

# Create a socket object
client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

# Connect to the target
client.connect((target_host, target_port))

# Send the malicious payload
payload = b"PUT_MALICIOUS_PAYLOAD_HERE"
client.send(payload)

# Close the connection
client.close()

original references:

- TrendMicro Zero Day Initiative (ZDI)
- Exim Security Advisory

Mitigation

To protect your Exim installations against this vulnerability, it is essential to apply the security patches provided by the vendors and regularly update your systems. Some mitigation steps include:

Update Exim to the latest version as soon as possible.

2. Restrict access to the SMTP service by implementing an access control list (ACL). This will limit the exposure of the vulnerability to the attackers.

Conclusion

CVE-2023-42117 - Exim Improper Neutralization of Special Elements Remote Code Execution Vulnerability is a critical vulnerability that allows remote attackers to execute arbitrary code on affected installations of Exim. By exploiting the lack of proper validation of user-supplied data within the smtp service, attacker can achieve remote code execution in the context of the targeted process. It is crucial to take steps to mitigate the risk of this vulnerability by maintaining up-to-date systems and controlling access to the smtp service.

Timeline

Published on: 05/03/2024 03:15:50 UTC