Juniper Junos OS/Junos OS Evolved prior 22.4R3-S5/23.2R2-S3/23.4R2-S4/24.2R2 Layer 2 Address Learning Daemon memory leak

Summaryinfo

A vulnerability classified as problematic has been found in Juniper Junos OS and Junos OS Evolved. This vulnerability affects unknown code of the component Layer 2 Address Learning Daemon. Performing a manipulation results in memory leak. This vulnerability was named CVE-2026-33780. The attack needs to be approached within the local network. There is no available exploit. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical has been found in Juniper Junos OS and Junos OS Evolved. This affects some unknown processing of the component Layer 2 Address Learning Daemon. The manipulation with an unknown input leads to a memory leak vulnerability. CWE is classifying the issue as CWE-401. The product does not sufficiently track and release allocated memory after it has been used, which slowly consumes remaining memory. This is going to have an impact on availability. The summary by CVE is:

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.

The advisory is shared at kb.juniper.net. This vulnerability is uniquely identified as CVE-2026-33780 since 03/23/2026. The exploitability is told to be easy. Access to the local network is required for this attack to succeed. No form of authentication is needed for exploitation. Neither technical details nor an exploit are publicly available.

Upgrading to version 22.4R3-S5, 23.2R2-S3, 23.4R2-S4 or 24.2R2 eliminates this vulnerability.

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Productinfo

Type

• Router Operating System

Vendor

• Juniper

Name

• Junos OS
• Junos OS Evolved

License

• commercial

Website

• Vendor: https://www.juniper.net/

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