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Vulnerability details: VCID-j2jz-uxem-rucp
Vulnerability ID VCID-j2jz-uxem-rucp
Aliases CVE-2021-21809
GHSA-c7jj-vfmr-j9mj
Summary Incorrect Permission Assignment for Critical Resource A command execution vulnerability exists in the default legacy spellchecker plugin in Moodle A specially crafted series of HTTP requests can lead to command execution. An attacker must have administrator privileges to exploit this vulnerabilities.
Status Published
Exploitability 0.5
Weighted Severity 9.0
Risk 4.5
Affected and Fixed Packages Package Details
Weaknesses (4)
CWE-1035 OWASP Top Ten 2017 Category A9 - Using Components with Known Vulnerabilities
CWE-78 Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
CWE-937 OWASP Top Ten 2013 Category A9 - Using Components with Known Vulnerabilities
CWE-732 Incorrect Permission Assignment for Critical Resource
System Score Found at
cvssv3.1 9.1 http://packetstormsecurity.com/files/164481/Moodle-SpellChecker-Path-Authenticated-Remote-Command-Execution.html
generic_textual CRITICAL http://packetstormsecurity.com/files/164481/Moodle-SpellChecker-Path-Authenticated-Remote-Command-Execution.html
epss 0.72901 https://api.first.org/data/v1/epss?cve=CVE-2021-21809
cvssv3.1 9.1 https://github.com/moodle/moodle
generic_textual CRITICAL https://github.com/moodle/moodle
cvssv3.1 9.1 https://nvd.nist.gov/vuln/detail/CVE-2021-21809
generic_textual CRITICAL https://nvd.nist.gov/vuln/detail/CVE-2021-21809
cvssv3.1 9.1 https://talosintelligence.com/vulnerability_reports/TALOS-2021-1277
generic_textual CRITICAL https://talosintelligence.com/vulnerability_reports/TALOS-2021-1277
Reference id Reference type URL
http://packetstormsecurity.com/files/164481/Moodle-SpellChecker-Path-Authenticated-Remote-Command-Execution.html
https://api.first.org/data/v1/epss?cve=CVE-2021-21809
https://github.com/moodle/moodle
https://talosintelligence.com/vulnerability_reports/TALOS-2021-1277
CVE-2021-21809 https://nvd.nist.gov/vuln/detail/CVE-2021-21809
Data source Metasploit
Description Moodle allows an authenticated administrator to define spellcheck settings via the web interface. An administrator can update the aspell path to include a command injection. This is extremely similar to CVE-2013-3630, just using a different variable. This module was tested against Moodle version 3.11.2, 3.10.0, and 3.8.0.
Note 
Stability:
  - crash-safe
Reliability:
  - repeatable-session
SideEffects:
  - config-changes
  - ioc-in-logs
Ransomware campaign use Unknown
Source publication date June 22, 2021
Platform PHP
Source URL https://github.com/rapid7/metasploit-framework/tree/master/modules/exploits/multi/http/moodle_spelling_path_rce.rb
Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H Found at http://packetstormsecurity.com/files/164481/Moodle-SpellChecker-Path-Authenticated-Remote-Command-Execution.html
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H Found at https://github.com/moodle/moodle
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H Found at https://nvd.nist.gov/vuln/detail/CVE-2021-21809
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H Found at https://talosintelligence.com/vulnerability_reports/TALOS-2021-1277
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Exploit Prediction Scoring System (EPSS)
Percentile 0.98799
EPSS Score 0.72901
Published At June 4, 2026, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2026-06-04T16:21:33.944758+00:00 GitLab Importer Import https://gitlab.com/gitlab-org/advisories-community/-/blob/main/packagist/moodle/moodle/CVE-2021-21809.yml 38.6.0