An improper check for unusual or exceptional conditions vulnerability in Juniper Networks MX Series platforms with Trio-based MPC (Modular Port Concentrator) deployed in (Ethernet VPN) EVPN-(Virtual Extensible LAN) VXLAN configuration, may allow an attacker sending specific Layer 2 traffic to cause Distributed Denial of Service (DDoS) protection to trigger unexpectedly, resulting in traffic impact.

Continued receipt and processing of this specific Layer 2 frames will sustain the Denial of Service (DoS) condition.

An indication of compromise is to check DDOS LACP violations:

user@device> show ddos-protection protocols statistics brief | match lacp

This issue only affects the MX Series platforms with Trio-based MPC. No other products or platforms are affected.

This issue affects:

Juniper Networks Junos OS on MX Series:

• 15.1 versions prior to 15.1R7-S9;
• 17.3 versions prior to 17.3R3-S11;
• 17.4 versions prior to 17.4R3-S4;
• 18.1 versions prior to 18.1R3-S12;
• 18.2 versions prior to 18.2R2-S8, 18.2R3-S8;
• 18.3 versions prior to 18.3R3-S4;
• 18.4 versions prior to 18.4R1-S8, 18.4R2-S7, 18.4R3-S7;
• 19.1 versions prior to 19.1R3-S4;
• 19.2 versions prior to 19.2R1-S6;
• 19.3 versions prior to 19.3R3-S2;
• 19.4 versions prior to 19.4R2-S4, 19.4R3-S2;
• 20.1 versions prior to 20.1R2, 20.1R3;
• 20.2 versions prior to 20.2R2-S1, 20.2R3;
• 20.3 versions prior to 20.3R1-S1, 20.3R2;

The DDoS feature is enabled by default, there is no specific config stanza required to enable DDoS protection.

The example of EVPN-VXLAN configuration stanza affected by this issue is as follows:

[protocols evpn]

[routing-instances <name> protocols evpn]

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-2021-0228 .

The following software releases have been updated to resolve this specific issue: 15.1R7-S9, 17.3R3-S11, 17.4R3-S4, 18.1R3-S12, 18.2R2-S8, 18.2R3-S8, 18.3R3-S4, 18.4R1-S8, 18.4R2-S7, 18.4R3-S7, 19.1R3-S4, 19.2R1-S6, 19.3R3-S2, 19.4R2-S4, 19.4R3-S2, 20.1R2, 20.1R3, 20.2R2-S1, 20.2R3, 20.3R1-S1, 20.3R2, 20.4R1, and all subsequent releases.

This issue is being tracked as 1512033 .

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

DDoS for LACP can be disabled:

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-2021-0228 at cve.mitre.org