CVE-2018-0056 Explained : Impact and Mitigation

When a duplicate MAC address is detected by two different interfaces on an MX Series device, the MAC address learning function properly switches between the interfaces. However, there is a possibility that the Layer 2 Address Learning Daemon (L2ALD) daemon may crash when trying to remove the duplicate MAC address if the specific entry is not found in the internal MAC address table. This issue is only observed on MX Series devices with l2-backhaul VPN configuration. No other products or platforms are affected by this problem.

Understanding CVE-2018-0056

This CVE affects Juniper Networks' Junos OS on MX Series devices.

What is CVE-2018-0056?

CVE-2018-0056 is a vulnerability in the L2ALD daemon on MX Series devices that may crash when encountering a duplicate MAC address scenario.

The Impact of CVE-2018-0056

CVSS Base Score: 6.5 (Medium Severity)
Attack Vector: Adjacent Network
Availability Impact: High
Attack Complexity: Low
No Confidentiality or Integrity Impact
No Privileges Required
No User Interaction Required
Scope: Unchanged
The vulnerability could lead to a denial of service if exploited.

Technical Details of CVE-2018-0056

This section provides more in-depth technical insights into the vulnerability.

Vulnerability Description

The L2ALD daemon on MX Series devices may crash when attempting to delete a duplicate MAC address without finding the specific entry in the internal MAC address table.

Affected Systems and Versions

Affected Platforms: MX Series
Affected Product: Junos OS
Vulnerable Versions: 15.1 to 18.1 on MX Series

Exploitation Mechanism

The vulnerability occurs when a duplicate MAC address is learned by two different interfaces on an MX Series device with l2-backhaul VPN configured.

Mitigation and Prevention

To address CVE-2018-0056, follow these mitigation strategies:

Immediate Steps to Take

Update affected software releases to the fixed versions provided by Juniper Networks.

Long-Term Security Practices

Regularly monitor and update network configurations to prevent MAC address conflicts.
Implement network segmentation to contain potential vulnerabilities.

Patching and Updates

Apply the recommended software releases to resolve the specific issue.