CVE-2026-33780: Junos OS and Junos OS Evolved: In an EVPN-MPLS scenario churn of ESI routes causes a memory leak in l2ald

A Missing Release of Memory after Effective Lifetime vulnerability in the Layer 2 Address Learning Daemon (l2ald) of Juniper Networks Junos OS and Junos OS Evolved allows an adjacent, unauthenticated attacker to cause a memory leak ultimately leading to a Denial of Service (DoS).

In an EVPN-MPLS scenario, routes learned from remote multi-homed Provider Edge (PE) devices are programmed as ESI routes. Due to a logic issue in the l2ald memory management, memory allocated for these routes is not released when there is churn for these routes. As a result, memory leaks in the l2ald process which will ultimately lead to a crash and restart of l2ald.

Use the following command to monitor the memory consumption by l2ald:

user@device> show system process extensive | match "PID|l2ald"

This issue affects:

Junos OS:

all versions before 22.4R3-S5, 23.2 versions before 23.2R2-S3, 23.4 versions before 23.4R2-S4, 24.2 versions before 24.2R2;

Junos OS Evolved:

all versions before 22.4R3-S5-EVO, 23.2 versions before 23.2R2-S3-EVO, 23.4 versions before 23.4R2-S4-EVO, 24.2 versions before 24.2R2-EVO.