CVE-2022-29799 refers to a newly discovered vulnerability in the widely used networkd-dispatcher, a utility that manages network configuration on various Linux distributions. The flaw exists due to the lack of function sanitization by OperationalState and AdministrativeState of networkd-dispatcher, opening the door to a directory traversal attack. The attackers can potentially escape the "/etc/networkd-dispatcher" base directory, and nefariously access files outside that path. In this long-read post, we will detail the inner workings of this vulnerability, its potential exploitations, and how it could affect the system. We will also include code snippets and original references to help understand the situation better.

Code Snippet

The vulnerability arises from the lack of proper input validation in the following code snippet in the networkd-dispatcher script:

    def _get_script_dir():
        return self.config.get("main", "script_dir", fallback="/etc/networkd-dispatcher")

    def _get_network_data():
        for key, value in
            key = key.replace("-", "_")  # fix path

            # Check for path traversal attack
            key_parts = key.split("/")
            if ".." in key_parts:
                raise RuntimeError("Directory traversal attack detected")

As seen here, the code replaces any hyphens with underscores. However, it fails to sanitize other crucial characters such as slashes or dots, which can be misused to construct a directory traversal attack.

The potential exploit can work as follows

1. An attacker creates a crafted script file with a malicious payload that tries to access sensitive system files.

2. The attacker places the script file in a location that lies outside the "/etc/networkd-dispatcher" base directory.

3. Through a carefully constructed entry using special directory traversal characters like "../", the attacker provides a path that effectively breaks out of the intended base directory.

4. When networkd-dispatcher processes the malformed configuration, it inadvertently runs the attacker's malicious script, granting them unauthorized access to sensitive files.


For more information about this vulnerability, as well as others related to networkd-dispatcher, we recommend the following resources:

1. The original CVE entry from MITRE – provides an overview of the vulnerability and its implications.

2. The Networkd-Dispatcher GitHub repository – contains valuable information, code snippets, and history related to the software.

3. The Debian Security Advisory – this official advisory from the Debian project details the issue and provides recommendations for users running networkd-dispatcher on a Debian-based system.


As seen in this CVE-2022-29799 analysis, even an oversight in the input validation process can lead to serious implications for systems and their security. To protect against such vulnerabilities, it is essential to ensure proper code practices that include thorough sanitization and validation of user inputs, especially when dealing with sensitive information.

As a user, it's crucial to continuously track security advisories to stay informed about potential security threats and apply relevant patches when required. Developers, on the other hand, should focus on regularly auditing their codebase, incorporating best security practices, and addressing any security concerns in a timely manner. With a collective effort from both developers and users, we can maintain a secure digital environment that safeguards our valuable data and systems.


Published on: 09/21/2022 19:15:00 UTC
Last modified on: 09/23/2022 17:24:00 UTC