# CVE-2020-7777: Arbitrary Code Execution

> Attackers can execute arbitrary JavaScript code by providing a malicious schema file to the jsen library, requiring immediate mitigation or replacement.

- **Severity:** High 7.2 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H/E:P/RL:U/RC:C`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 23 Nov 2020
- **Updated:** 17 Sep 2024
- **Also known as:** GHSA-vm64-cfqx-3698

## What is CVE-2020-7777?

CVE-2020-7777 is a high-severity code injection vulnerability in jsen, published on 23 Nov 2020. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

This affects all versions of package jsen. If an attacker can control the schema file, it could run arbitrary JavaScript code on the victim machine. In the module description and README file there is no mention about the risks of untrusted schema files, so I assume that this is applicable. In particular the required field of the schema is not properly sanitized. The resulting string that is build based on the schema definition is then passed to a Function.apply();, leading to an Arbitrary Code Execution.

## Which versions are affected by CVE-2020-7777?

2 open source packages ship an affected version, including jsen. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `jsen` | npm | All versions to 0.6.6 | None |
| `jsen` | npm | All versions to 0.6.6 | None |

Products: Jsen Project Jsen.

## How do I fix CVE-2020-7777?

No fix has been published for CVE-2020-7777 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-7777 being exploited?

There is no known exploitation of CVE-2020-7777 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-7777 and fix it if it is affected.

What it is: CVE-2020-7777 is a high-severity code injection vulnerability in jsen, published on 23 Nov 2020. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2020-7777 in the wild and no public exploit code.

Affected packages and fixed versions:
- jsen (npm): affected all versions up to 0.6.6; no fix listed
- jsen (npm): affected all versions up to 0.6.6; no fix listed

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-2020-7777/ (Markdown: https://insights.sbomify.com/CVE-2020-7777/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-7777
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-7777
- OSV: https://osv.dev/vulnerability/CVE-2020-7777

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-7777/
Summaries are generated and may contain mistakes; the official description above is the record.