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Vulnerability record · CVE-2021-21809 · published 23 June 2021

CVE-2021-21809: Moodle os command injection vulnerability

Moodle · Moodle

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.

9.1 CVSS 3.1 Critical EPSS 24% · top 2.2% CWE-78 · OS command injection
9.1CVSS 3.1 base score, v2 9.0
24%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References, 4 tagged exploit
17 Jun 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
http://packetstormsecurity.com/files/164481/Moodle-SpellChecker-Path-Authenticated-Remote-Command-Execution.html ExploitThird Party AdvisoryVDB Entry
https://talosintelligence.com/vulnerability_reports/TALOS-2021-1277 ExploitThird Party Advisory
http://packetstormsecurity.com/files/164481/Moodle-SpellChecker-Path-Authenticated-Remote-Command-Execution.html ExploitThird Party AdvisoryVDB Entry
https://talosintelligence.com/vulnerability_reports/TALOS-2021-1277 ExploitThird Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

10.0CVE-2019-3809Moodle cross-site request forgery vulnerabilityA flaw was found in Moodle versions 3.1 to 3.1.15 and earlier unsupported versions. The mybackpack functionality allowed setting the URL of badges, w…EPSS 0.86%10.0CVE-2006-4935Moodle improper input validation vulnerabilityThe Database module in Moodle before 1.6.2 does not properly handle uploaded files, which has unspecified impact and remote attack vectors.EPSS 1.5%10.0CVE-2006-4936Moodle improper input validation vulnerabilityMoodle before 1.6.2 does not properly validate the module instance id when creating a course module object, which has unspecified impact and remote a…EPSS 1.5%10.0CVE-2005-2247Moodle vulnerabilityMultiple unknown vulnerabilities in Moodle before 1.5.1 have unknown impact and attack vectors.EPSS 1.5%10.0CVE-2004-2233Moodle vulnerabilityUnknown "front page vulnerability with Moodle servers" for Moodle before 1.3.2 has unknown impact and attack vectors.EPSS 1.7%10.0CVE-2004-2235Moodle vulnerabilityUnknown vulnerability in Moodle before 1.2 has unknown impact and attack vectors, related to improper filtering of text.EPSS 1.4%10.0CVE-2004-2236Moodle vulnerabilityUnknown vulnerability in Moodle before 1.3.3 has unknown impact and attack vectors, related to language setting.EPSS 1.4%10.0CVE-2004-2237Moodle vulnerabilityUnknown vulnerability in Moodle before 1.3.4 has unknown impact and attack vectors, related to "strings in Moodle texts."EPSS 1.7%

Source: NIST National Vulnerability Database (record CVE-2021-21809), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.