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

> An adjacent attacker can cause a memory leak in the l2ald process via ESI route churn, leading to a denial of service.

- **Severity:** High 7.1 (`CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/AU:Y/RE:M`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 9 Apr 2026
- **Updated:** 13 Apr 2026
- **Also known as:** GHSA-wcmx-9w9j-q7ph

## What is CVE-2026-33780?

CVE-2026-33780 is a high-severity denial of service vulnerability in Juniper Junos, published on 9 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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.

Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime)

## Which versions are affected by CVE-2026-33780?

It affects 2 products.


Products: Juniper Junos, Juniper Junos Os Evolved.

## How do I fix CVE-2026-33780?

No fix has been published for CVE-2026-33780 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-33780 being exploited?

There is no known exploitation of CVE-2026-33780 in the wild and no public exploit code.

## Other vulnerabilities in Juniper Junos

- [CVE-2023-36845](https://insights.sbomify.com/CVE-2023-36845/): Juniper Junos OS EX Series and SRX Series PHP External Variable Modification (critical 9.8, exploited in the wild)
- [CVE-2020-1631](https://insights.sbomify.com/CVE-2020-1631/): Juniper Junos OS Path Traversal (high 8.8, exploited in the wild)
- [CVE-2025-21590](https://insights.sbomify.com/CVE-2025-21590/): Juniper Junos OS Improper Isolation or Compartmentalization (medium 6.7, exploited in the wild)
- [CVE-2023-36851](https://insights.sbomify.com/CVE-2023-36851/): Juniper Junos OS SRX Series Missing Authentication for Critical Function (medium 5.3, exploited in the wild)
- [CVE-2023-36844](https://insights.sbomify.com/CVE-2023-36844/): Juniper Junos OS EX Series PHP External Variable Modification (medium 5.3, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-33780 and fix it if it is affected.

What it is: CVE-2026-33780 is a high-severity denial of service vulnerability in Juniper Junos, published on 9 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-33780 in the wild and no public exploit code.

Affected product: Juniper Junos. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-33780/ (Markdown: https://insights.sbomify.com/CVE-2026-33780/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-33780
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-33780
- OSV: https://osv.dev/vulnerability/CVE-2026-33780

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-33780/
Summaries are generated and may contain mistakes; the official description above is the record.