A significant vulnerability (CVE-2024-9407) has been discovered recently in the bind-propagation option of the Dockerfile RUN --mount instruction, allowing attackers to exploit the system in various ways. This vulnerability arises due to improper input validation, resulting in users being able to pass arbitrary parameters to the mount instruction during the building process. In some cases, sensitive directories from the host can be mounted into a container, which could lead to unauthorized access or modification of the mounted files. Surprisingly, even if the system is using SELinux for protection, this vulnerability can bypass it, further escalating the potential risks. This article aims to provide a detailed analysis of this vulnerability, along with code snippets, links to original references, and exploit details.

The Vulnerability

Dockerfile is a crucial component in creating Docker containers, specifying the instructions for building and running an application. One of the essential instructions in a Dockerfile is RUN --mount, which is responsible for mounting filesystems during the build process. When using bind-propagation, the system does not adequately validate input passed to the --mount option, leading to this vulnerability.

An attacker can exploit this vulnerability to modify the contents of host files, potentially undermining the container's security and even affecting other containers running on the same host. Consequently, it poses a substantial threat to both the host system and the applications running within the containers.

Suppose a Dockerfile uses the following instruction for building the container

RUN --mount=type=bind,src=.,dst=/app,readonly [...]

An attacker can provide a specially crafted bind-propagation option, as seen below

RUN --mount=type=bind,src=.,dst=/app,bind-propagation=[Arbitrary_Parameter] [...]

By doing so, the attacker can mount sensitive host directories into a container, potentially accessing or modifying the mounted files.

For more in-depth knowledge about this vulnerability, please refer to the following sources

1. https://www.docker.com/security/cve-2024-#####
3. [NIST National Vulnerability Database](https://nvd.nist.gov/vuln/detail/CVE-2024-######" rel="nofollow">Original GitHub Issue

Exploiting the Vulnerability

To exploit this vulnerability, an attacker must first gain control of the Dockerfile or manipulate the building process input, enabling them to introduce arbitrary parameters to the bind-propagation option. Following this, the attacker can modify the Dockerfile RUN --mount instruction accordingly, as shown in the code snippet above. It allows them to gain unauthorized access to sensitive host files, modify their contents, or potentially compromise the container's security.

Conclusion

In summary, the CVE-2024-9407 vulnerability poses a significant threat to the security of the Docker environment. It is critical for developers and administrators to keep their Docker installations updated and incorporate necessary security measures to mitigate the risks associated with this vulnerability. Being aware of such vulnerabilities and their exploitation techniques is crucial in securing the rapidly growing container ecosystem.

Timeline

Published on: 10/01/2024 21:15:08 UTC
Last modified on: 12/31/2024 14:24:55 UTC