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CVE-2021-20187

23
FAUCET Score

CVE-2021-20187 describes a critical vulnerability in Moodle versions prior to 3.10.1, 3.9.4, 3.8.7, and 3.5.16, allowing site administrators to execute arbitrary PHP scripts during Shibboleth authentication. This vulnerability carries a high CVSS score of 7.2, indicating a severe impact with high confidentiality, integrity, and availability compromise possible, requiring high privileges but no user interaction. While the vulnerability is significant, there is no evidence of active exploitation, no known public exploit code (Metasploit, Nuclei, ExploitDB), and it is not listed in CISA's KEV catalog. Community discussion and media coverage are minimal, suggesting limited public awareness or active threat.

Impacted Technologies

VendorProductVersion(s)CPE
< 3.5.16CPE matchmatch criteria
cpe:2.3:a:moodle:moodle:*:*:*:*:*:*:*:*
>= 3.8.0, < 3.8.7CPE matchmatch criteria
cpe:2.3:a:moodle:moodle:*:*:*:*:*:*:*:*
>= 3.9.0, < 3.9.4CPE matchmatch criteria
cpe:2.3:a:moodle:moodle:*:*:*:*:*:*:*:*
3.10.0CPE matchmatch criteria
cpe:2.3:a:moodle:moodle:3.10.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.2HIGH

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
HIGH
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
1.2
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.57%
Probability of exploitation in next 30 days
EPSS Percentile
72.9%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0157 is in the 67th percentile among its peer group of 5,538 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.3 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (4)

composerpatch availablevia ghsa
Product: moodle/moodleFixed in: 3.5.16
composerpatch availablevia ghsa
Product: moodle/moodleFixed in: 3.8.7
composerpatch availablevia ghsa
Product: moodle/moodleFixed in: 3.9.4
composerpatch availablevia ghsa
Product: moodle/moodleFixed in: 3.10.1

Vendor Advisories (1)

composerGHSA-2jrm-gww7-wch2high

Moodle Arbitrary PHP code execution by site admins via Shibboleth configuration

May 24, 2022

References

moodle.org / mod/forum/discuss.php
PatchVendor Advisory