An Uncontrolled Resource Consumption vulnerability in Juniper Networks Junos OS on EX2300, EX3400 and EX4300 Series platforms allows an adjacent attacker sending a stream of layer 2 frames will trigger an Aggregated Ethernet (AE) interface to go down and thereby causing a Denial of Service (DoS).

By continuously sending a stream of specific layer 2 frames an attacker will sustain the Denial of Service (DoS) condition.

This issue affects:

Juniper Networks Junos OS EX4300 Series

• All versions prior to 15.1R7-S7;
• 16.1 versions prior to 16.1R7-S8;
• 17.1 versions prior to 17.1R2-S12;
• 17.2 versions prior to 17.2R3-S4;
• 17.3 versions prior to 17.3R3-S8;
• 17.4 versions prior to 17.4R2-S10, 17.4R3-S2;
• 18.1 versions prior to 18.1R3-S10;
• 18.2 versions prior to 18.2R2-S7, 18.2R3-S3;
• 18.3 versions prior to 18.3R2-S4, 18.3R3-S2;
• 18.4 versions prior to 18.4R1-S7, 18.4R2-S4, 18.4R3-S1;
• 19.1 versions prior to 19.1R1-S5, 19.1R2-S1, 19.1R3;
• 19.2 versions prior to 19.2R1-S5, 19.2R2;
• 19.3 versions prior to 19.3R2-S2, 19.3R3;
• 19.4 versions prior to 19.4R1-S2, 19.4R2.

Juniper Networks Junos OS EX3400 and EX4300-MP Series

• All versions prior to 18.1R3-S12;
• 18.2 versions prior to 18.2R3-S7;
• 18.3 versions prior to 18.3R3-S4;
• 18.4 versions prior to 18.4R2-S9, 18.4R3-S7;
• 19.1 versions prior to 19.1R2-S3, 19.1R3-S4;
• 19.2 versions prior to 19.2R3-S1;
• 19.3 versions prior to 19.3R3-S1;
• 19.4 versions prior to 19.4R3-S1;
• 20.1 versions prior to 20.1R3;
• 20.2 versions prior to 20.2R3;
• 20.3 versions prior to 20.3R2.

Juniper Networks Junos OS EX2300 Series

• All versions prior to 18.3R3-S5;
• 18.4 versions prior to 18.4R2-S9, 18.4R3-S9;
• 19.1 versions prior to 19.1R2-S3, 19.1R3-S6;
• 19.2 versions prior to 19.2R1-S7, 19.2R3-S3;
• 19.3 versions prior to 19.3R2-S7, 19.3R3-S3;
• 19.4 versions prior to 19.4R3-S5;
• 20.1 versions prior to 20.1R2-S2, 20.1R3-S1;
• 20.2 versions prior to 20.2R3-S2;
• 20.3 versions prior to 20.3R3-S1;
• 20.4 versions prior to 20.4R2-S1, 20.4R3;
• 21.1 versions prior to 21.1R2.

This issue can only occur when the device is configured with Link Aggregation Control Protocol (LACP) in combination with Link Layer Discovery Protocol (LLDP).

The examples of minimum config stanza affected by this issue:

in combination with:

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-2021-31365 .

The following software releases have been updated to resolve this specific issue in Junos OS

- For EX4300 Series: 15.1R7-S7, 16.1R7-S8, 17.1R2-S12, 17.2R3-S4, 17.3R3-S8, 17.4R2-S10, 17.4R3-S2, 18.1R3-S10, 18.2R2-S7, 18.2R3-S3, 18.3R2-S4, 18.3R3-S2, 18.4R1-S7, 18.4R2-S4, 18.4R3-S1, 19.1R1-S5, 19.1R2-S1, 19.1R3, 19.2R2, 19.3R2-S2, 19.3R3, 19.4R1-S2, 19.4R2, 20.1R1, and all subsequent releases.

- For EX3400 and EX4300-MP Series: 18.1R3-S12, 18.2R3-S7, 18.3R3-S4, 18.4R2-S9, 18.4R3-S7, 19.1R2-S3, 19.1R3-S4, 19.2R3-S1, 19.3R3-S1, 19.4R3-S1, 20.1R3, 20.2R3, 20.3R2, 20.4R1, and all subsequent releases.

-For EX2300 Series: 18.3R3-S5, 18.4R2-S9, 18.4R3-S9, 19.1R2-S3, 19.1R3-S6, 19.2R1-S7, 19.2R3-S3, 19.3R2-S7, 19.3R3-S3, 19.4R3-S5, 20.1R2-S2, 20.1R3-S1, 20.2R3-S2, 20.3R3-S1, 20.4R2-S1, 20.4R3, 21.1R2, 21.2R1, and all subsequent releases.

This issue is being tracked as  1481911 ,  1582255  and  1542530 .

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

2021-10-13: 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 Vulnerability - How to Contact the Juniper Networks Security Incident Response Team
• CVE-2021-31365: Junos OS: EX2300, EX3400, EX4300 and EX4400 Series: An Aggregated Ethernet (AE) interface will go down due to a stream of specific layer 2 frames