When a MX Series is configured as a Broadband Network Gateway (BNG) based on Layer 2 Tunneling Protocol (L2TP), executing certain CLI command may cause the system to run out of disk space, excessive disk usage may cause other complications.

An administrator can use the following CLI command to monitor the available disk space:

This issue affects Juniper Networks Junos OS on MX Series:

• 17.3R1 and later versions prior to 17.4R3-S5,
• 18.1 versions prior to 18.1R3-S13,
• 18.2 versions prior to 18.2R3-S7;
• 18.3 versions prior to 18.3R3-S4;
• 18.4 versions prior to 18.4R3-S7;
• 19.1 versions prior to 19.1R3-S4;
• 19.2 versions prior to 19.2R1-S6, 19.2R3-S2;
• 19.3 versions prior to 19.3R3-S2;
• 19.4 versions prior to 19.4R2-S4, 19.4R3-S2;
• 20.1 versions prior to 20.1R3;
• 20.2 versions prior to 20.2R2-S3, 20.2R3;
• 20.3 versions prior to 20.3R2;
• 20.4 versions prior to 20.4R1-S1, 20.4R2;

This issue does not affect Juniper Networks Junos OS versions prior to 17.3R1.

Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

This issue was seen during production usage.

This issue has been assigned CVE-2021-0238 .

The following software releases have been updated to resolve this specific issue: 17.4R3-S5, 18.1R3-S13, 18.2R3-S7, 18.3R3-S4, 18.4R3-S7, 19.1R3-S4, 19.2R1-S6, 19.2R3-S2, 19.3R3-S2, 19.4R2-S4, 19.4R3-S2, 20.1R3, 20.2R2-S3, 20.2R3, 20.3R2, 20.4R1-S1, 20.4R2, 21.1R1, and all subsequent releases.

If impacted, issue is recoverable after restarting the jl2tpd daemon:

This issue is being tracked as 1537772 .

Software releases or updates are available for download at https://support.juniper.net/support/downloads/

There are no viable workarounds for this issue.

To reduce the risk of exploitation of this issue, use access lists or firewall filters to limit access to the CLI only trusted administrative networks, hosts and users.

2021-04-14: Initial Publication.

• KB16613: Overview of the Juniper Networks SIRT Quarterly Security Bulletin Publication Process [juniper.net]
• KB16765: In which releases are vulnerabilities fixed? [juniper.net]
• KB16446: Common Vulnerability Scoring System (CVSS) and Juniper's Security Advisories [juniper.net]
• Report a Security Vulnerability - How to Contact the Juniper Networks Security Incident Response Team
• CVE-2021-0238 at cve.mitre.org