# CVE-2023-36835: Denial of service in Junos OS

> A network-based attacker can cause a persistent denial of service on Juniper QFX10000 switches by sending a specific IP packet routed over VXLAN.

- **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:** 14 Jul 2023
- **Updated:** 7 Nov 2024
- **Also known as:** GHSA-3xwf-x58p-42cm

## What is CVE-2023-36835?

CVE-2023-36835 is a high-severity denial of service vulnerability in Juniper Junos, published on 14 Jul 2023. 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 the Packet Forwarding Engine (PFE) of Juniper Networks Junos OS on QFX10000 Series allows a network based attacker to cause a Denial of Service (DoS).

If a specific valid IP packet is received and that packet needs to be routed over a VXLAN tunnel, this will result in a PFE wedge condition due to which traffic gets impacted. As this is not a crash and restart scenario, this condition will persist until the system is rebooted to recover.

This issue affects Juniper Networks Junos OS on QFX10000:
20.3 version 20.3R1 and later versions;
20.4 versions prior to 20.4R3-S5;
21.1 versions prior to 21.1R3-S5;
21.2 versions prior to 21.2R3-S5;
21.3 versions prior to 21.3R3-S4;
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-S2, 22.3R2.

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

## Which versions are affected by CVE-2023-36835?

It affects 1 product.


Products: Juniper Junos.

## How do I fix CVE-2023-36835?

No fix has been published for CVE-2023-36835 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-36835 being exploited?

There is no known exploitation of CVE-2023-36835 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-2023-36835 and fix it if it is affected.

What it is: CVE-2023-36835 is a high-severity denial of service vulnerability in Juniper Junos, published on 14 Jul 2023. 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-2023-36835 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-2023-36835/ (Markdown: https://insights.sbomify.com/CVE-2023-36835/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-36835
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-36835
- OSV: https://osv.dev/vulnerability/CVE-2023-36835

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-36835/
Summaries are generated and may contain mistakes; the official description above is the record.