# CVE-2021-31357: Junos OS Evolved: shell-injection vulnerabilities in evo_tcpdump UI wrapper script

> Authenticated attackers can inject shell commands via tcpdump wrapper to bypass CLI restrictions and execute arbitrary commands.

- **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:** 17 Sep 2024
- **Also known as:** GHSA-6hf2-h4c4-m3pw

## What is CVE-2021-31357?

CVE-2021-31357 is a high-severity command injection vulnerability in Juniper Junos Os Evolved, 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 command injection vulnerability in tcpdump command processing on Juniper Networks Junos OS Evolved allows an attacker with authenticated CLI access to be able to bypass configured access protections to execute arbitrary shell commands within the context of the current user. The vulnerability allows an attacker to bypass command authorization restrictions assigned to their specific user account and execute commands that are available to the privilege level for which the user is assigned. For example, a user that is in the super-user login class, but restricted to executing specific CLI commands could exploit the vulnerability to execute any other command available to an unrestricted admin user. This vulnerability does not increase the privilege level of the user, but rather bypasses any CLI command restrictions by allowing full access to the shell. This issue affects Juniper Networks Junos OS Evolved: All versions prior to 20.3R2-S1-EVO; 20.4 versions prior to 20.4R2-S2-EVO; 21.1 versions prior to 21.1R2-EVO; 21.2 versions prior to 21.2R1-S1-EVO, 21.2R2-EVO.

Weakness: CWE-78 (Improper Neutralization of Special Elements used in an OS Command), CWE-77 (Improper Neutralization of Special Elements used in a Command)

## Which versions are affected by CVE-2021-31357?

It affects 1 product.


Products: Juniper Junos Os Evolved.

## How do I fix CVE-2021-31357?

No fix has been published for CVE-2021-31357 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-31357 being exploited?

There is no known exploitation of CVE-2021-31357 in the wild and no public exploit code.

## Other vulnerabilities in Juniper Junos Os Evolved

- [CVE-2026-21902](https://insights.sbomify.com/CVE-2026-21902/): Junos OS Evolved: PTX Series: A vulnerability allows a unauthenticated, network-based attacker to execute code as root (critical 9.3)
- [CVE-2023-28983](https://insights.sbomify.com/CVE-2023-28983/): Junos OS Evolved: Shell Injection vulnerability in the gNOI server (high 8.8)
- [CVE-2025-21599](https://insights.sbomify.com/CVE-2025-21599/): Denial of service in Junos OS Evolved (high 8.7)
- [CVE-2024-47502](https://insights.sbomify.com/CVE-2024-47502/): Junos OS Evolved: TCP session state is not always cleared on the Routing Engine leading to DoS (high 8.7)
- [CVE-2024-39531](https://insights.sbomify.com/CVE-2024-39531/): Junos OS Evolved: ACX 7000 Series: Protocol specific DDoS configuration affects other protocols (high 8.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-31357 and fix it if it is affected.

What it is: CVE-2021-31357 is a high-severity command injection vulnerability in Juniper Junos Os Evolved, 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-2021-31357 in the wild and no public exploit code.

Affected product: Juniper Junos Os Evolved. 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-2021-31357/ (Markdown: https://insights.sbomify.com/CVE-2021-31357/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-31357
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-31357
- OSV: https://osv.dev/vulnerability/CVE-2021-31357

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-31357/
Summaries are generated and may contain mistakes; the official description above is the record.