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Introduction

A vulnerability (CVE-2024-1488) was discovered in Unbound, the widely-used open-source DNS resolver software. This vulnerability stems from incorrect default permissions settings, which can open the door for unauthorized processes outside the Unbound group to alter the runtime configuration of the unbound.service.

By connecting over localhost to the exposed port 8953, an attacker could potentially manipulate the running instance of Unbound. This can lead to several consequences, such as:

1. Altering the forwarders, allowing the attacker to monitor all queries forwarded by the local resolver.

In some cases, completely disrupting the DNS resolving process, rendering it non-functional.

This article dives into a detailed analysis of the CVE-2024-1488 vulnerability, provides code snippets to demonstrate the issue, and links to original references for further understanding.

Code Snippet

The following Python code snippet demonstrates how any local process can connect and interact with the Unbound Control API on port 8953:

import socket

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect(('localhost', 8953))

commands = ['list_forwards', 'forward_remove']
for command in commands:
    sock.sendall(f'{command}\n'.encode())
    response = sock.recv(4096).decode()
    print(response)

sock.close()

The code demonstrates connecting to the Unbound Control API and listing the current forwards, as well as modifying the forwards.

Exploit Details

The exploitation of the CVE-2024-1488 vulnerability is made possible due to the incorrect default permissions settings. To mitigate this vulnerability:

Update Unbound to the latest version

- The developers of Unbound have released an updated version of the software to address this vulnerability.
- Download the latest Unbound version

Adjust permissions for the Unbound Control Port

- Secure the control port by modifying unbound.conf and setting the correct permissions. For example, restrict connections to the control port by updating the following settings:

Original References

For more information regarding this vulnerability and its impact, please refer to the following sources:

1. Vulnerability Note VU#234605 - This vulnerability note provides a brief description of the vulnerability and the affected software versions.
2. Unbound Security Advisory - An official security advisory published by the Unbound team detailing the vulnerability and available patches.
3. Unbound Github Repository - The official Github repository for Unbound, where you can view the latest source code, issues, and updates.

In conclusion, the CVE-2024-1488 vulnerability exposes Unbound instances to unauthorized access and configuration changes. Users are urged to update their software, modify default system permissions, and limit control access, in order to mitigate this vulnerability.

Timeline

Published on: 02/15/2024 05:15:10 UTC
Last modified on: 04/15/2024 04:15:14 UTC