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CVE-2021-21809

53
FAUCET Score

CVE-2021-21809 is a critical command execution vulnerability affecting Moodle 3.10's default legacy spellchecker plugin. An attacker with administrator privileges can exploit this by sending specially crafted HTTP requests, leading to full system compromise. With a CVSS score of 9.1 and an EPSS percentile of 0.72129, this vulnerability presents a significant risk, despite requiring high privileges for exploitation. While not observed in active exploitation, a Metasploit module exists, indicating readily available exploit code, though community discussion and media coverage remain low.

Impacted Technologies

VendorProductVersion(s)CPE
3.10.0CPE matchmatch criteria
cpe:2.3:a:moodle:moodle:3.10.0:-:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

8.2HIGH

CVSS:3.0/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:L/A:L

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
HIGH
User Interaction
NONE
Scope
CHANGED
Confidentiality Impact
HIGH
Integrity Impact
LOW
Availability Impact
LOW
Exploitability Score
2.3
Impact Score
5.3
CvssVersion
3.0

Exploit Intelligence

EPSS Score
24.17%
Probability of exploitation in next 30 days
EPSS Percentile
97.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
Metasploit: Moodle SpellChecker Path Authenticated Remote Command Execution · Jun 22, 2021
This CVE's current EPSS score of 0.2417 is in the 98th percentile among its peer group of 464 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.7 Bluesky, 0.4 Mastodon, and 1.7 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.4 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Advisories (1)

composerGHSA-c7jj-vfmr-j9mjcritical

Moodle command execution vulnerability exists in the default legacy spellchecker plugin

May 24, 2022

References

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