CVE-2021-21809Public exploitNetwork attack vector

Administrator command execution via injected aspell path

Published Jun 23, 2021 · Updated Aug 3, 2024

Command injection in Moodle LMS 3.10 allows remote authenticated users with administrator privileges to execute server commands. PSpellShell inserts the administrator-controlled aspellpath value into a shell_exec command without neutralizing backtick shell syntax. Exploitation requires an administrator to select PSpellShell and store a crafted path; the resulting commands run as the web-server account.

CVSS severity8.2
High
EPSS probability24.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Command injection in Moodle LMS 3.10 allows remote authenticated users with administrator privileges to execute server commands. PSpellShell inserts the administrator-controlled aspellpath value into a shell_exec command without neutralizing backtick shell syntax. Exploitation requires an administrator to select PSpellShell and store a crafted path; the resulting commands run as the web-server account.

The record

CVE
CVE-2021-21809
Published
Jun 23, 2021
Updated
Aug 3, 2024
Vendor
Moodle
Product
Moodle LMS
Classifications
CWE-78, T1059.004
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Jun 23, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=Moodle 3.10

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Moodle · Moodle LMSversion=Moodle 3.10

Published CVSS scores

9.0NIST NVDAV:N/AC:L/Au:S/C:C/I:C/A:C
8.2Cisco TalosCVSS:3.0/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:L/A:L
9.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-78Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
T1059.004Command and Scripting Interpreter: Unix Shell

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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