# CVE-2021-20099: Privilege escalation in Nessus Agent

> Local administrators can escalate privileges to run executables as the Nessus host service, requiring an upgrade to remediate.

- **Severity:** Medium 6.7 (`CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 28 Jun 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-3fcp-gh22-82v3

## What is CVE-2021-20099?

CVE-2021-20099 is a medium-severity vulnerability in Tenable Nessus, published on 28 Jun 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Nessus Agent 8.2.4 and earlier for Windows were found to contain multiple local privilege escalation vulnerabilities which could allow an authenticated, local administrator to run specific Windows executables as the Nessus host. This is different than CVE-2021-20100.

## Which versions are affected by CVE-2021-20099?

It affects 1 product.


Products: Tenable Nessus.

## How do I fix CVE-2021-20099?

No fix has been published for CVE-2021-20099 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-20099 being exploited?

There is no known exploitation of CVE-2021-20099 in the wild and no public exploit code.

## Other vulnerabilities in Tenable Nessus

- [CVE-2022-4313](https://insights.sbomify.com/CVE-2022-4313/): Command injection in Tenable.io, Tenable.sc and Nessus (high 8.8)
- [CVE-2023-0524](https://insights.sbomify.com/CVE-2023-0524/): Privilege escalation in Tenable.io, Tenable.sc, Nessus (high 8.8)
- [CVE-2023-0101](https://insights.sbomify.com/CVE-2023-0101/): Privilege escalation in Nessus (high 8.8)
- [CVE-2022-32973](https://insights.sbomify.com/CVE-2022-32973/): Privilege escalation in Nessus (high 8.8)
- [CVE-2025-36630](https://insights.sbomify.com/CVE-2025-36630/): Local Privilege Escalation (high 8.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-20099 and fix it if it is affected.

What it is: CVE-2021-20099 is a medium-severity vulnerability in Tenable Nessus, published on 28 Jun 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-2021-20099 in the wild and no public exploit code.

Affected product: Tenable Nessus. 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-2021-20099/ (Markdown: https://insights.sbomify.com/CVE-2021-20099/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-20099
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-20099
- OSV: https://osv.dev/vulnerability/CVE-2021-20099

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-20099/
Summaries are generated and may contain mistakes; the official description above is the record.