# CVE-2021-20076: Deserialization in Tenable.sc

> An authenticated unprivileged user can achieve remote code execution on the Tenable.sc server via unsafe PHP unserialization.

- **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:** 3 Mar 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-3ccq-6jj2-4rxc

## What is CVE-2021-20076?

CVE-2021-20076 is a high-severity unsafe deserialization vulnerability in Tenable.sc, published on 3 Mar 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Tenable.sc and Tenable.sc Core versions 5.13.0 through 5.17.0 were found to contain a vulnerability that could allow an authenticated, unprivileged user to perform Remote Code Execution (RCE) on the Tenable.sc server via Hypertext Preprocessor unserialization.

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2021-20076?

It affects 1 product.


Products: Tenable Tenable.sc.

## How do I fix CVE-2021-20076?

No fix has been published for CVE-2021-20076 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-20076 being exploited?

There is no known exploitation of CVE-2021-20076 in the wild and no public exploit code.

## Other vulnerabilities in Tenable.sc

- [CVE-2022-0130](https://insights.sbomify.com/CVE-2022-0130/): File upload in Tenable.sc (high 8.1)
- [CVE-2020-5808](https://insights.sbomify.com/CVE-2020-5808/): Missing authorization in Tenable.sc (high 7.5)
- [CVE-2023-0476](https://insights.sbomify.com/CVE-2023-0476/): Other in Tenable.sc (medium 6.5)
- [CVE-2023-24495](https://insights.sbomify.com/CVE-2023-24495/): Server-side request forgery in Tenable.sc (medium 6.5)
- [CVE-2023-24493](https://insights.sbomify.com/CVE-2023-24493/): Code injection in Tenable.sc (medium 5.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-20076 and fix it if it is affected.

What it is: CVE-2021-20076 is a high-severity unsafe deserialization vulnerability in Tenable.sc, published on 3 Mar 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-2021-20076 in the wild and no public exploit code.

Affected product: Tenable.sc. 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-2021-20076/ (Markdown: https://insights.sbomify.com/CVE-2021-20076/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-20076
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-20076
- OSV: https://osv.dev/vulnerability/CVE-2021-20076

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-20076/
Summaries are generated and may contain mistakes; the official description above is the record.