Moodle
CVE-2021-21809
CRITICAL
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V1 - Encoding and Sanitization OS command sanitization, avoid shell exec
MITRE ATT&CK
2 techniques across 1 tactic: Execution The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Impact | CVSS score of 9.1 (CRITICAL). Attack characteristics: network attack vector, low complexity, high privileges required, no user interaction not required. Public proof-of-concept exploit code is available. |
| Exploit ScenarioDerived | A remote attacker could execute arbitrary operating system commands on the host by sending crafted requests to the affected application. |
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Alert meAnalysisAI
A command execution vulnerability exists in the default legacy spellchecker plugin in Moodle 3.10. Rated critical severity (CVSS 9.1), this vulnerability is remotely exploitable, low attack complexity. Public exploit code available and no vendor patch available.
RemediationAI
No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Avoid passing user input to shell commands. Use language-specific APIs instead of shell execution. Apply strict input validation with allowlists.
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 1 package in composer
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
This vulnerability is classified as OS Command Injection (CWE-78), which allows attackers to execute arbitrary operating system commands on the host. 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. Affected products include: Moodle.
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
DescriptionNVD
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.
Threat Intelligence Overview
NVD
CVE.org
EPSS
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
OS command injection occurs when an application passes unsanitized user input directly into system shell commands.
Affected Products (CPE)NVD
Moodle through 2.5.2 allows remote authenticated administrators to execute arbitrary programs by configuring the aspell
A flaw was found in Moodle. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authenticatio
In Moodle 2.x and 3.x, SQL injection can occur via user preferences. Rated critical severity (CVSS 9.8), this vulnerabil
The Moodle LMS Jmol plugin version 6.1 and earlier contains a path traversal vulnerability in jsmol.php. The query param
Multiple cross-site scripting (XSS) vulnerabilities in Moodle through 2.2.11, 2.3.x before 2.3.9, 2.4.x before 2.4.6, an
Unrestricted file upload vulnerability in the double extension support in the "image" module in Moodle 3.1.2 allows remo
Unrestricted file upload vulnerability in the "legacy course files" and "file manager" modules in Moodle 3.1.2 allows re
moodle before versions 3.5.2, 3.4.5, 3.3.8, 3.1.14 is vulnerable to an XML import of ddwtos could lead to intentional re
An issue was discovered in Moodle 3.x. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, low a
Moodle 3.1.2 allows remote attackers to obtain sensitive information via unspecified vectors, related to a "SQL Injectio
Moodle 3.10.3 contains a persistent cross-site scripting vulnerability in the calendar event subtitle field that allows
Directory traversal vulnerability in repository/filesystem/lib.php in Moodle through 2.2.11, 2.3.x before 2.3.10, 2.4.x
GitHub PoC
Exploit-DB