CVE-2018-6556 Explained : Impact and Mitigation

A vulnerability in the lxc-user-nic component of LXC allows unprivileged users to open arbitrary files, potentially leading to unauthorized access and unintended consequences.

Understanding CVE-2018-6556

The lxc-user-nic command, when used to remove a network interface, can be exploited by users with limited privileges to access paths they should not be able to reach.

What is CVE-2018-6556?

The vulnerability in LXC's lxc-user-nic component enables unprivileged users to open specified paths, potentially revealing sensitive information and causing unintended system changes.

The Impact of CVE-2018-6556

This vulnerability allows unauthorized users to access restricted paths and trigger read-only openings of critical kernel files, leading to potential security breaches and system instability.

Technical Details of CVE-2018-6556

The technical aspects of the vulnerability in the lxc-user-nic component of LXC.

Vulnerability Description

The lxc-user-nic command, when instructed to remove a network interface, will automatically open a path specified by the user. This code path can be exploited by a user with limited privileges to verify the existence of a path they would otherwise not be able to access. Additionally, it has the potential to cause unintended consequences by initiating a read-only opening of certain kernel files (such as ptmx, proc, sys).

Affected Systems and Versions

Affected versions include LXC versions 2.0 and above, starting from 2.0.9, as well as versions 3.0 and above, prior to 3.0.2.

Exploitation Mechanism

The vulnerability allows unprivileged users to open arbitrary files, potentially leading to unauthorized access and system compromise.

Mitigation and Prevention

Steps to mitigate and prevent the CVE-2018-6556 vulnerability.

Immediate Steps to Take

Update LXC to versions 2.0.9 or above for 2.0 branch and 3.0.2 or above for 3.0 branch to address the vulnerability.
Monitor system logs for any suspicious activities related to unauthorized file access.

Long-Term Security Practices

Implement proper access controls and user permissions to restrict file access.
Regularly update and patch LXC and other software components to prevent security vulnerabilities.

Patching and Updates

Apply patches provided by LXC to fix the vulnerability and enhance system security.