# CVE-2024-21616: Junos OS: MX Series and SRX Series: Processing of a specific SIP packet causes NAT IP allocation to fail

> An unauthenticated attacker can cause a sustained Denial of Service by sending specific SIP packets when SIP ALG is enabled on Juniper MX and SRX devices.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 12 Jan 2024
- **Updated:** 17 Jun 2025
- **Also known as:** GHSA-355p-vp22-pp2v

## What is CVE-2024-21616?

CVE-2024-21616 is a high-severity denial of service vulnerability in Juniper Junos, published on 12 Jan 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An Improper Validation of Syntactic Correctness of Input vulnerability in Packet Forwarding Engine (PFE) of Juniper Networks Junos OS allows an unauthenticated, network-based attacker to cause Denial of Service (DoS).

On all Junos OS MX Series and SRX Series platforms, when SIP ALG is enabled, and a specific SIP packet is received and processed, NAT IP allocation fails for genuine traffic, which causes Denial of Service (DoS). Continuous receipt of this specific SIP ALG packet will cause a sustained DoS condition.

NAT IP usage can be monitored by running the following command.

user@srx> show security nat resource-usage source-pool <source_pool_name>

Pool name: source_pool_name
..
Address Factor-index Port-range Used Avail Total Usage
X.X.X.X
0 Single Ports 50258 52342 62464 96% <<<<<
- Alg Ports 0 2048 2048 0%
This issue affects:

Juniper Networks Junos OS on MX Series and SRX Series

  *  All versions earlier than 21.2R3-S6;
  *  21.3 versions earlier than 21.3R3-S5;
  *  21.4 versions earlier than 21.4R3-S5;
  *  22.1 versions earlier than 22.1R3-S4;
  *  22.2 versions earlier than 22.2R3-S3;
  *  22.3 versions earlier than 22.3R3-S1;
  *  22.4 versions earlier than 22.4R2-S2, 22.4R3;
  *  23.2 versions earlier than 23.2R1-S1, 23.2R2.

Weakness: CWE-1286 (Improper Validation of Syntactic Correctness of Input)

## Which versions are affected by CVE-2024-21616?

It affects 1 product.


Products: Juniper Junos.

## How do I fix CVE-2024-21616?

No fix has been published for CVE-2024-21616 yet. Limit exposure of the affected software until one is available.

## Is CVE-2024-21616 being exploited?

There is no known exploitation of CVE-2024-21616 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-2024-21616 and fix it if it is affected.

What it is: CVE-2024-21616 is a high-severity denial of service vulnerability in Juniper Junos, published on 12 Jan 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-2024-21616 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-2024-21616/ (Markdown: https://insights.sbomify.com/CVE-2024-21616/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-21616
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-21616
- OSV: https://osv.dev/vulnerability/CVE-2024-21616

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-21616/
Summaries are generated and may contain mistakes; the official description above is the record.