CVE-2023-23923 — moodle/moodle
HIGHCVE-2023-23923 is a high-severity (CVSS 8.2) CWE-284 vulnerability in moodle/moodle. A fix is available for moodle/moodle — see the affected versions and patch details below.
Moodle: possible to set the preferred "start page" of other users
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-23923.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2023-23923 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
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
The vulnerability was found Moodle which exists due to insufficient limitations on the "start page" preference. A remote attacker can set that preference for another user. The vulnerability allows a remote attacker to gain unauthorized access to otherwise restricted functionality.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | moodle/moodle | all versions | 3.9.19composer require moodle/moodle:^3.9.19 |
| 🐘Packagist | moodle/moodle | ≥ 3.10.0&&< 3.11.12 | 3.11.12composer require moodle/moodle:^3.11.12 |
| 🐘Packagist | moodle/moodle | ≥ 4.0.0-beta&&< 4.0.6 | 4.0.6composer require moodle/moodle:^4.0.6 |
| 🐘Packagist | moodle/moodle | ≥ 4.1.0-beta&&< 4.1.1 | 4.1.1composer require moodle/moodle:^4.1.1 |
Detection & 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 3.9.19 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-23923 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2023-23923 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2023-23923. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2023-23923 in your dependencies?
O3 Security finds CVE-2023-23923 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.