An exploitable vulnerability has been identified in NetworkManager-libreswan client plugin, which allows unprivileged users to escalate their privileges and potentially execute code as root by abusing special characters in the VPN configuration. Specifically, this security flaw is triggered by improper sanitization of the VPN configuration created by unprivileged users, causing the application to interpret values as keys.
Exploit Details
The vulnerability arises from the improper handling of special characters in VPN configuration set by an unprivileged user when using the libreswan client plugin for NetworkManager (NetworkManager-libreswan). In the key-value format of the VPN configuration, the plugin does not escape special characters correctly. Consequently, this allows certain values to be interpreted as keys within the application.
One of the most critical parameters that a malicious user can abuse is the leftupdown key. This key accepts an executable command and is used by NetworkManager-libreswan to specify a callback setting for retrieving configuration settings from NetworkManager.
Here's an example of how the affected parameter looks in the configuration
conn my-vpn
... (other configuration settings)
leftupdown="/path/to/executable script.sh"
As NetworkManager utilizes Polkit to grant unprivileged users the ability to control the system's network configuration, a malicious actor can exploit this flaw to escalate their privileges locally and potentially execute arbitrary code as root on the targeted machine.
To perform the exploit, the attacker would need to create a malicious configuration file with the leftupdown key pointing to a malicious script. This script would then be executed with root privileges during a VPN connection attempt.
An example exploit script might look similar to this
#!/bin/bash
echo 'This is a malicious script.'
echo 'malicious_command' | tee -a log.txt
touch /root/malicious_file
And the VPN configuration file would have the following configuration
conn my-vpn
... (other configuration settings)
leftupdown="/path/to/malicious script.sh"
Mitigation
As of this writing, there is no official patch available for this vulnerability. However, users can take some precautionary measures such as:
Restricting access to leftupdown key to authorized users only.
3. Implementing proper input validation and sanitization measures while working with VPN configurations.
References
1. Original Security Advisory
2. NetworkManager-libreswan GitHub Repository
3. Polkit Documentation
4. CVE-2024-9050 Information
Timeline
Published on: 10/22/2024 13:15:02 UTC
Last modified on: 12/18/2024 17:15:15 UTC