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Vulnerabilities

Vulnerability · CVE-2021-21809

A command execution vulnerability exists in the default legacy spellchecker plugin in Moodle 3.10.

Published Jun 23, 2021 · catalog updated Jun 17, 2026 · A command execution vulnerability

Last checked Nov 7, 2026. A connected source was read within the last 7 days.

Check this week

CVE-2021-21809 is not in CISA KEV. FIRST estimates a 24.17% chance of exploitation in the next 30 days. Check whether you run A command execution vulnerability.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (A command execution vulnerability).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
Critical9.1
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
24.17%
Remediation
Advisory link
Affected products
cpe 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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe moodle/moodle3.10.0

How to fix CVE-2021-21809

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2021-21809 is not in CISA KEV. FIRST estimates a 24.17% chance of exploitation in the next 30 days. Check whether you run A command execution vulnerability.

Which versions are affected?

Compare what you have installed with 3.10.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-78: OS Command Injection. EPSS 24.17%. There is no CISA KEV listing. A public exploit reference is linked in Sources. That is not the same as confirmed exploitation. Use the source links for the original advisory.

Technology hubs

Moodle security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Jun 23, 2021 · Monitored products — high

    Detected

    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.

  2. Jun 17, 2026 · Monitored products — high

    Updated

    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.

Sources

  • CVE.orgVulnerability recordCVE-2021-21809

    Official CVE identifier

    cve.org
  • Monitored products — highVendor advisoryCVE-2021-21809

    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.

    nvd.nist.gov
  • Metasploit ModulesPublic exploit moduleexploit_multi/http/moodle_spelling_path_rce

    Public module reference (excellent). Module source is not copied into this catalog.

    rapid7.com
  • Packet Storm SecurityCited referencehttp://packetstormsecurity.com/files/164481/Moodle-SpellChecker-Path-Authenticated-Remote-Command-Execution.html

    Packet Storm link already published on the finding.

    packetstormsecurity.com

References

Freshness

Last verified in this catalog Nov 4, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • Metasploit ModulesNov 7, 2026
  • Packet Storm SecurityNov 7, 2026
  • CVE.orgNov 4, 2026
  • Monitored products — highNov 4, 2026