A Use-After-Free vulnerability in the Layer 2 Address Learning Daemon (l2ald) of Juniper Networks Junos OS and Junos OS Evolved allows an unauthenticated, adjacent attacker to cause l2ald to crash leading to a Denial-of-Service (DoS).

In an EVPN-VXLAN scenario, when state updates are received and processed by the affected system, the correct order of some processing steps is not ensured, which can lead to an l2ald crash and restart. Whether the crash occurs depends on system internal timing which is outside the attackers control.

This issue affects:

Junos OS: 

• All versions before 20.4R3-S8,
• 21.2 versions before 21.2R3-S6,
• 21.3 versions before 21.3R3-S5,
• 21.4 versions before 21.4R3-S4,
• 22.1 versions before 22.1R3-S3,
• 22.2 versions before 22.2R3-S1,
• 22.3 versions before 22.3R3,,
• 22.4 versions before 22.4R2;

Junos OS Evolved: 

• All versions before 20.4R3-S8-EVO,
• 21.2 versions before 21.2R3-S6-EVO, 
• 21.3 versions before 21.3R3-S5-EVO,
• 21.4 versions before 21.4R3-S4-EVO,
• 22.1 versions before 22.1R3-S3-EVO,
• 22.2 versions before 22.2R3-S1-EVO,
• 22.3 versions before 22.3R3-EVO,
• 22.4 versions before 22.4R2-EVO.

To be exposed to this issue the device must be configured for EVPN-VXLAN. Refer to product documentation for how to configure EVPN-VXLAN as there are different configuration options.

The following software releases have been updated to resolve this specific issue:
Junos OS: 20.4R3-S8, 21.2R3-S6, 21.3R3-S5, 21.4R3-S4, 21.4R3-S5, 22.1R3-S3, 22.2R3-S1, 22.3R3, 22.3R3-S2, 22.4R2, 23.2R1, and all subsequent releases;
Junos OS Evolved: 20.4R3-S8-EVO, 21.2R3-S6-EVO, 21.3R3-S5-EVO, 21.4R3-S4-EVO, 22.1R3-S3-EVO, 22.2R3-S1-EVO, 22.3R3-EVO, 22.4R2-EVO, 23.2R1-EVO, and all subsequent releases.

This issue is being tracked as 1700170 which is visible on the Customer Support website.

Note: Juniper SIRT's policy is not to evaluate releases which are beyond End of Engineering (EOE) or End of Life (EOL).

2024-04-10 - Initial Publication
2024-04-11 - added the affected component in the first sentence of the problem statement
2024-09-13: Minor formatting change to CVSS field

• 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