# CVE-2025-21599: Denial of service in Junos OS Evolved

> Unauthenticated attackers can cause kernel memory exhaustion and system crashes by sending malformed IPv6 packets to Junos OS Evolved devices.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 9 Jan 2025
- **Updated:** 9 Jan 2025
- **Also known as:** GHSA-p34f-rw7f-c723

## What is CVE-2025-21599?

CVE-2025-21599 is a high-severity denial of service vulnerability in Juniper Junos Os Evolved, published on 9 Jan 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A Missing Release of Memory after Effective Lifetime vulnerability in the Juniper Tunnel Driver (jtd) of Juniper Networks Junos OS Evolved allows an unauthenticated network-based attacker to cause Denial of Service. 

Receipt of specifically malformed IPv6 packets, destined to the device, causes kernel memory to not be freed, resulting in memory exhaustion leading to a system crash and Denial of Service (DoS). Continuous receipt and processing of these packets will continue to exhaust kernel memory, creating a sustained Denial of Service (DoS) condition.
This issue only affects systems configured with IPv6.

This issue affects Junos OS Evolved: 

  *  from 22.4-EVO before 22.4R3-S5-EVO, 
  *  from 23.2-EVO before 23.2R2-S2-EVO, 
  *  from 23.4-EVO before 23.4R2-S2-EVO, 
  *  from 24.2-EVO before 24.2R1-S2-EVO, 24.2R2-EVO.

This issue does not affect Juniper Networks Junos OS Evolved versions prior to 22.4R1-EVO.

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

## Which versions are affected by CVE-2025-21599?

It affects 1 product.


Products: Juniper Junos Os Evolved.

## How do I fix CVE-2025-21599?

No fix has been published for CVE-2025-21599 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-21599 being exploited?

There is no known exploitation of CVE-2025-21599 in the wild and no public exploit code.

## Other vulnerabilities in Juniper Junos Os Evolved

- [CVE-2026-21902](https://insights.sbomify.com/CVE-2026-21902/): Junos OS Evolved: PTX Series: A vulnerability allows a unauthenticated, network-based attacker to execute code as root (critical 9.3)
- [CVE-2023-28983](https://insights.sbomify.com/CVE-2023-28983/): Junos OS Evolved: Shell Injection vulnerability in the gNOI server (high 8.8)
- [CVE-2024-47502](https://insights.sbomify.com/CVE-2024-47502/): Junos OS Evolved: TCP session state is not always cleared on the Routing Engine leading to DoS (high 8.7)
- [CVE-2024-39531](https://insights.sbomify.com/CVE-2024-39531/): Junos OS Evolved: ACX 7000 Series: Protocol specific DDoS configuration affects other protocols (high 8.7)
- [CVE-2024-39562](https://insights.sbomify.com/CVE-2024-39562/): Junos OS Evolved: A high rate of SSH connections causes a Denial of Service (high 8.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-21599 and fix it if it is affected.

What it is: CVE-2025-21599 is a high-severity denial of service vulnerability in Juniper Junos Os Evolved, published on 9 Jan 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-21599 in the wild and no public exploit code.

Affected product: Juniper Junos Os Evolved. 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-2025-21599/ (Markdown: https://insights.sbomify.com/CVE-2025-21599/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-21599
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-21599
- OSV: https://osv.dev/vulnerability/CVE-2025-21599

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-21599/
Summaries are generated and may contain mistakes; the official description above is the record.