# CVE-2021-31372: Junos OS: J-Web allows a locally authenticated attacker to escalate their privileges to root.

> A locally authenticated attacker can exploit improper input validation in J-Web to escalate privileges to root on Juniper Junos OS devices.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/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:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 19 Oct 2021
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-86jj-q96q-44q7

## What is CVE-2021-31372?

CVE-2021-31372 is a high-severity vulnerability in Juniper Junos, published on 19 Oct 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

An Improper Input Validation vulnerability in J-Web of Juniper Networks Junos OS allows a locally authenticated J-Web attacker to escalate their privileges to root over the target device. This issue affects: Juniper Networks Junos OS All 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 19.2R3-S3; 19.3 versions prior to 19.3R3-S3; 19.4 versions prior to 19.4R3-S5; 20.1 versions prior to 20.1R3-S1; 20.2 versions prior to 20.2R3-S2; 20.3 versions prior to 20.3R3-S1; 20.4 versions prior to 20.4R3; 21.1 versions prior to 21.1R2, 21.1R3; 21.2 versions prior to 21.2R1-S1, 21.2R2;

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2021-31372?

It affects 1 product.


Products: Juniper Junos.

## How do I fix CVE-2021-31372?

No fix has been published for CVE-2021-31372 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-31372 being exploited?

There is no known exploitation of CVE-2021-31372 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-2021-31372 and fix it if it is affected.

What it is: CVE-2021-31372 is a high-severity vulnerability in Juniper Junos, published on 19 Oct 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-31372 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-2021-31372/ (Markdown: https://insights.sbomify.com/CVE-2021-31372/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-31372
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-31372
- OSV: https://osv.dev/vulnerability/CVE-2021-31372

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-31372/
Summaries are generated and may contain mistakes; the official description above is the record.