CVE-2023-25809 : Exploit Details and Defense Strategies

This CVE-2023-25809 was published on March 29, 2023, by GitHub_M, indicating a vulnerability in the "rootless" aspect of runc related to the improper preservation of permissions in certain conditions.

Understanding CVE-2023-25809

The vulnerability identified as CVE-2023-25809 affects the runc CLI tool used for spawning and running containers according to the OCI specification. It involves the incorrect handling of permissions within the '/sys/fs/cgroup' directory under specific circumstances, potentially allowing a container to gain unauthorized write access to specific cgroup hierarchies on the host.

What is CVE-2023-25809?

In affected versions of rootless runc, the '/sys/fs/cgroup' directory becomes writable when runc is executed within or outside the user namespace under certain configurations. This could lead to a container being able to modify user-owned cgroup hierarchies on the host, enabling unauthorized access.

The Impact of CVE-2023-25809

The impact of this vulnerability is rated as MEDIUM with a CVSS base score of 5.0. The attack complexity is high, requiring local access and high privileges. However, the availability, integrity, and confidentiality impacts are assessed as low.

Technical Details of CVE-2023-25809

The vulnerability description outlines the specific scenarios under which the '/sys/fs/cgroup' directory becomes writable, potentially compromising cgroup hierarchies. The affected systems include versions of runc prior to 1.1.5.

Vulnerability Description

The vulnerability arises from rootless runc making '/sys/fs/cgroup' writable when executed within specific user namespaces or under specific mount configurations, allowing unauthorized write access to user-owned cgroup directories.

Affected Systems and Versions

The vulnerability impacts versions of runc that are older than 1.1.5. Users with these versions are at risk of cgroup hierarchy compromise if the improper permissions preservation occurs.

Exploitation Mechanism

By exploiting this vulnerability, a container could gain unauthorized write access to designated cgroup hierarchies within the '/sys/fs/cgroup' directory on the host, potentially leading to security breaches and unauthorized system manipulation.

Mitigation and Prevention

To address CVE-2023-25809 and mitigate its impact, users and administrators are advised to take immediate steps to secure their systems and prevent unauthorized access.

Immediate Steps to Take

Upgrade to version 1.1.5 of runc to address the vulnerability and prevent unauthorized write access to cgroup hierarchies.
If upgrading is not feasible, consider unsharing the cgroup namespace or adding '/sys/fs/cgroup' to 'maskedPaths' as alternative mitigation measures to limit unauthorized access.

Long-Term Security Practices

In the long term, it is crucial to stay updated on security advisories and promptly apply patches or updates to mitigate emerging vulnerabilities effectively. Regular security audits and configuration reviews can also help in identifying and addressing potential security gaps.

Patching and Updates

Ensure regular monitoring of software updates and security advisories related to runc and similar containerization tools to apply patches promptly. Keeping systems up to date with the latest software versions is key to maintaining a secure and resilient environment.