# CVE-2023-36834: Denial of service in Junos OS

> An adjacent attacker can cause a denial of service on Juniper SRX firewalls configured in L2 transparent mode by sending specific packets that loop processing engines.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:A/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:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 14 Jul 2023
- **Updated:** 22 Oct 2024
- **Also known as:** GHSA-6cxr-6qqw-c9xc

## What is CVE-2023-36834?

CVE-2023-36834 is a medium-severity denial of service vulnerability in Juniper Junos, published on 14 Jul 2023. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

An Incomplete Internal State Distinction vulnerability in the packet forwarding engine (PFE) of Juniper Networks Junos OS on SRX 4600 and SRX 5000 Series allows an adjacent attacker to cause a Denial of Service (DoS).

If an SRX is configured in L2 transparent mode the receipt of a specific genuine packet can cause a single Packet Processing Engines (PPE) component of the PFE to run into a loop, which in turn will render the PPE unavailable. Each packet will cause one PPE to get into a loop, leading to a gradual performance degradation until all PPEs are unavailable and all traffic processing stops. To recover the affected FPC need to be restarted.

This issue affects Juniper Networks Junos OS on SRX 4600 and SRX 5000 Series:
20.1 version 20.1R1 and later versions;
20.2 versions prior to 20.2R3-S7;
20.3 version 20.3R1 and later versions;
20.4 versions prior to 20.4R3-S7;
21.1 versions prior to 21.1R3-S5;
21.2 versions prior to 21.2R3-S3;
21.3 versions prior to 21.3R3-S3;
21.4 versions prior to 21.4R3-S1;
22.1 versions prior to 22.1R3;
22.2 versions prior to 22.2R2;
22.3 versions prior to 22.3R1-S1, 22.3R2.

Weakness: CWE-372 (Incomplete Internal State Distinction)

## Which versions are affected by CVE-2023-36834?

It affects 1 product.


Products: Juniper Junos.

## How do I fix CVE-2023-36834?

No fix has been published for CVE-2023-36834 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-36834 being exploited?

There is no known exploitation of CVE-2023-36834 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-2023-36834 and fix it if it is affected.

What it is: CVE-2023-36834 is a medium-severity denial of service vulnerability in Juniper Junos, published on 14 Jul 2023. 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-2023-36834 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-2023-36834/ (Markdown: https://insights.sbomify.com/CVE-2023-36834/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-36834
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-36834
- OSV: https://osv.dev/vulnerability/CVE-2023-36834

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-36834/
Summaries are generated and may contain mistakes; the official description above is the record.