Moodle command execution vulnerability exists in the default legacy spellchecker plugin

published 2021-06-23 5 y ago modified 2026-09-08 2 mo ago also BIT-moodle-2021-21809 , EUVD-2022-3528 , GHSA-c7jj-vfmr-j9mj

cvss: 8.2; version 3.0, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 24.2%; EPSS 24.2% chance of exploitation in 30 days, percentile 97%
public exploits: 1; Metasploit

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.

Patch / fix

fixed in 1

bitnami moodle 3.10.1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-21809 updated 2025-11-21 cvss 8.2

moodle: specially crafted series of HTTP requests can lead to command execution

Red Hat All currently supported Red Hat products
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Timeline

2021-06-22 First public exploit (Metasploit exploit/multi/http/moodle_spelling_path_rce)
2021-06-23 Published

Exploit prediction

24.17% chance of exploitation in the next 30 days, higher than 97% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

Metasploit exploit/multi/http/moodle_spelling_path_rce Moodle SpellChecker Path Authenticated Remote Command Execution metasploit exploit, excellent rank, 2021-06-22
talosintelligence.com https://talosintelligence.com/vulnerability_reports/TALOS-2021-1277 referenced PoC, tagged "exploit" by a source, unverified
packetstormsecurity.com http://packetstormsecurity.com/files/164481/Moodle-SpellChecker-Path-Authenticated-Remote-Command-Execution.html referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	3.0	8.2	CVSS:3.0/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:L/A:L
GitHub	3.1	9.1	CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
NVD	3.1	9.1	CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
NVD	2.0	9.0	AV:N/AC:L/Au:S/C:C/I:C/A:C
OSV	3.1	9.1	CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

Affected packages

ecosystem	package	affected	fixed in
packagist	moodle/moodle	1 listed version	no fix listed
bitnami	moodle	>=3.10.0, <3.10.1	3.10.1

Affected products

n/a Moodle

Classification

Weakness

CWE-732 Incorrect Permission Assignment for Critical Resource
CWE-78 Improper Neutralization of Special Elements used in an OS Command

References

talosintelligence.com /vulnerability_reports/TALOS-2021-1277
web, exploit, third-party-advisory, advisory
packetstormsecurity.com /files/164481/Moodle-SpellChecker-Path-Authenticated-Remote-Command-Execution.html
web, exploit, third-party-advisory, vdb-entry, advisory
nvd.nist.gov /vuln/detail/CVE-2021-21809
advisory, web
github.com /moodle/moodle
package

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary