CVE-2021-20281 is a medium-severity (CVSS 5.3) Information Exposure vulnerability in moodle/moodle. A fix is available for moodle/moodle — see the affected versions and patch details below.
Moodle allowed some users without permission to view other users' full names
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-20281 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
moodle/moodle🐘moodle/moodle🐘moodle/moodle🐘moodle/moodleReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
It was possible for some users without permission to view other users' full names to do so via the online users block in moodle before 3.10.2, 3.9.5, 3.8.8, 3.5.17.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | moodle/moodle | ≥ 3.10.0&&< 3.10.2 | 3.10.2composer require moodle/moodle:^3.10.2 |
| 🐘Packagist | moodle/moodle | ≥ 3.9.0&&< 3.9.5 | 3.9.5composer require moodle/moodle:^3.9.5 |
| 🐘Packagist | moodle/moodle | ≥ 3.8.0&&< 3.8.8 | 3.8.8composer require moodle/moodle:^3.8.8 |
| 🐘Packagist | moodle/moodle | ≥ 3.5&&< 3.5.17 | 3.5.17composer require moodle/moodle:^3.5.17 |
Affected Products
fedorafedoraprojectmoodlemoodleDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for moodle/moodle, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update moodle/moodle to 3.10.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-20281 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
Frequently Asked Questions
Is CVE-2021-20281 in your dependencies?
Find it across Packagist, including transitive dependencies.