# CVE-2024-39559: Race condition in Junos OS Evolved

> An unauthenticated attacker can crash dual RE Junos OS Evolved systems with NSR enabled by sending specific TCP packets during a race condition window.

- **Severity:** High 8.2 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/R:A`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 10 Jul 2024
- **Updated:** 2 Aug 2024
- **Also known as:** GHSA-473h-3vgg-7379

## What is CVE-2024-39559?

CVE-2024-39559 is a high-severity vulnerability in Juniper Junos Os Evolved, published on 10 Jul 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An Improper Check for Unusual or Exceptional Conditions vulnerability in packet processing of Juniper Networks Junos OS Evolved may allow a network-based unauthenticated attacker to crash the device (vmcore) by sending a specific TCP packet over an established TCP session with MD5 authentication enabled, destined to an accessible port on the device, resulting in a Denial of Service (DoS).  The receipt of this packet must occur within a specific timing window outside the attacker's control (i.e., race condition).

Continued receipt and processing of this packet will create a sustained Denial of Service (DoS) condition.

This issue only affects dual RE systems with Nonstop Active Routing (NSR) enabled.
Exploitation can only occur over TCP sessions with MD5 authentication enabled (e.g., BGP with MD5 authentication).

This issue affects Junos OS Evolved: 

  *  All versions before 21.2R3-S8-EVO, 
  *  from 21.4-EVO before 21.4R3-S6-EVO, 
  *  from 22.1-EVO before 22.1R3-S4-EVO, 
  *  from 22.2-EVO before 22.2R3-S4-EVO, 
  *  from 22.3-EVO before 22.3R3-S3-EVO, 
  *  from 22.4-EVO before 22.4R2-S2-EVO, 22.4R3-EVO.

Weakness: CWE-754 (Improper Check for Unusual or Exceptional Conditions)

## Which versions are affected by CVE-2024-39559?

It affects 1 product.


Products: Juniper Junos Os Evolved.

## How do I fix CVE-2024-39559?

No fix has been published for CVE-2024-39559 yet. Limit exposure of the affected software until one is available.

## Is CVE-2024-39559 being exploited?

There is no known exploitation of CVE-2024-39559 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-2025-21599](https://insights.sbomify.com/CVE-2025-21599/): Denial of service in Junos OS Evolved (high 8.7)
- [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)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-39559 and fix it if it is affected.

What it is: CVE-2024-39559 is a high-severity vulnerability in Juniper Junos Os Evolved, published on 10 Jul 2024. 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-2024-39559 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-2024-39559/ (Markdown: https://insights.sbomify.com/CVE-2024-39559/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-39559
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-39559
- OSV: https://osv.dev/vulnerability/CVE-2024-39559

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-39559/
Summaries are generated and may contain mistakes; the official description above is the record.