# CVE-2021-31359: Junos OS and Junos OS Evolved: Local Privilege Escalation vulnerability

> A local low-privileged user can execute arbitrary commands as root or cause a denial of service in the Juniper DHCP daemon.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 19 Oct 2021
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-2m9j-6j4j-wm2c

## What is CVE-2021-31359?

CVE-2021-31359 is a high-severity vulnerability in Juniper Junos, published on 19 Oct 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A local privilege escalation vulnerability in Juniper Networks Junos OS and Junos OS Evolved allows a local, low-privileged user to cause the Juniper DHCP daemon (jdhcpd) process to crash, resulting in a Denial of Service (DoS), or execute arbitrary commands as root. Continued processing of malicious input will repeatedly crash the system and sustain the Denial of Service (DoS) condition. Systems are only vulnerable if jdhcpd is running, which can be confirmed via the 'show system processes' command. For example: root@host# run show system processes extensive | match dhcp 26537 root -16 0 97568K 13692K RUN 0 0:01 3.71% jdhcpd This issue affects: Juniper Networks Junos OS: All versions, including the following supported releases: 15.1 versions prior to 15.1R7-S10; 17.4 versions prior to 17.4R3-S5; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R3-S9; 19.1 versions prior to 19.1R3-S6; 19.2 versions prior to 19.2R1-S7, 19.2R3-S3; 19.3 versions prior to 19.3R2-S6, 19.3R3-S3; 19.4 versions prior to 19.4R3-S6; 20.1 versions prior to 20.1R2-S2, 20.1R3-S1; 20.2 versions prior to 20.2R3-S2; 20.3 versions prior to 20.3R3; 20.4 versions prior to 20.4R2-S1, 20.4R3; 21.1 versions prior to 21.1R1-S1, 21.1R2. Juniper Networks Junos OS Evolved: All versions prior to 20.4R2-S3-EVO; All versions of 21.1-EVO.

Weakness: CWE-269 (Improper Privilege Management), CWE-121 (Stack-based Buffer Overflow)

## Which versions are affected by CVE-2021-31359?

It affects 2 products.


Products: Juniper Junos, Juniper Junos Os Evolved.

## How do I fix CVE-2021-31359?

No fix has been published for CVE-2021-31359 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-31359 being exploited?

There is no known exploitation of CVE-2021-31359 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-2021-31359 and fix it if it is affected.

What it is: CVE-2021-31359 is a high-severity vulnerability in Juniper Junos, published on 19 Oct 2021. 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-2021-31359 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-2021-31359/ (Markdown: https://insights.sbomify.com/CVE-2021-31359/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-31359
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-31359
- OSV: https://osv.dev/vulnerability/CVE-2021-31359

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-31359/
Summaries are generated and may contain mistakes; the official description above is the record.