CVE-2021-21809

CRITICAL

Moodle Authenticated Spelling Binary RCE

Title source: metasploit
STIX 2.1

Exploitation Summary

EIP tracks 2 public exploits for CVE-2021-21809. PoCs published by anldori, Adam Reiser, h00die, including Metasploit module exploits/multi/http/moodle_spelling_path_rce.

AI-analyzed exploit summary This repository contains a functional exploit for CVE-2021-21809, a command execution vulnerability in Moodle's legacy spellchecker plugin. The exploit leverages administrator privileges to modify system paths and execute arbitrary commands via a reverse shell.

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.

Exploits (2)

nomisec WORKING POC 1 stars
by anldori · poc
https://github.com/anldori/CVE-2021-21809

This repository contains a functional exploit for CVE-2021-21809, a command execution vulnerability in Moodle's legacy spellchecker plugin. The exploit leverages administrator privileges to modify system paths and execute arbitrary commands via a reverse shell.

Classification
Working Poc 95%
Attack Type
Rce
Complexity
Moderate
Reliability
Reliable
Target: Moodle 3.10
Auth required
Prerequisites: Administrator credentials · Network access to the target
devstral-2 · analyzed Feb 18, 2026 Full analysis →
metasploit WORKING POC EXCELLENT
by Adam Reiser, h00die · rubypocphp
https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/multi/http/moodle_spelling_path_rce.rb

This Metasploit module exploits a command injection vulnerability in Moodle's spellcheck settings, allowing authenticated administrators to execute arbitrary commands by manipulating the aspell path. It triggers the payload via a spellcheck RPC call.

Classification
Working Poc 100%
Attack Type
Rce
Complexity
Moderate
Reliability
Reliable
Target: Moodle 3.0.0+
Auth required
Prerequisites: Authenticated admin access to Moodle · Spellcheck settings accessible
devstral-2 · analyzed Feb 16, 2026 Full analysis →

References (2)

Core 2
Core References
Exploit, Third Party Advisory x_refsource_misc
https://talosintelligence.com/vulnerability_reports/TALOS-2021-1277

Scores

CVSS v3 9.1
EPSS 0.7290
EPSS Percentile 98.8%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

Details

CWE
CWE-78
Status published
Products (2)
moodle/moodle 3.10.0
moodle/moodle Packagist
Published Jun 23, 2021
Tracked Since Feb 18, 2026