How severe is CVE-2011-4203?

No CVSS score has been assigned to CVE-2011-4203 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2011-4203?

CVE-2011-4203 affects the following packages: moodle/moodle (Packagist), moodle/moodle (Packagist), moodle/moodle (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2011-4203?

Update moodle/moodle to 1.9.15 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2011-4203 is resolved across your whole dependency graph.

How do I detect CVE-2011-4203 in my Packagist dependencies?

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.

How do I mitigate CVE-2011-4203 if there is no patch (or I can't update yet)?

Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.

Is CVE-2011-4203 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2011-4203, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2011-4203?

CVE-2011-4203 has an EPSS (Exploit Prediction Scoring System) score of 1.2%, placing it in the 68th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2011-4203?

CVE-2011-4203 is classified as Code Injection (CWE-94). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2011-4203 published, and has it been updated?

CVE-2011-4203 was published on May 13, 2022 and was last updated on January 17, 2024. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘 Packagist

Not in CISA KEV

CVE-2011-4203 — moodle

Fix: moodle/moodle@581e8db

CVE-2011-4203 is a Code Injection vulnerability in moodle/moodle. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for moodle/moodle — see the affected versions and patch details below.

Moodle CRLF Injection Vulnerability in Calendar Component

Published

May 13, 2022

Updated

Jan 17, 2024

Affected

3 pkgs

Patched

3 / 3

Exploits

1 known

Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs68th percentile — riskier than 68% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

3 pkgs affected

🐘moodle/moodle🐘moodle/moodle🐘moodle/moodle

Real-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

CRLF injection vulnerability in calendar/set.php in the Calendar component in Moodle 1.9.x before 1.9.15, 2.0.x before 2.0.6, 2.1.x before 2.1.3, and 2.2 allows remote attackers to inject arbitrary HTTP headers and conduct HTTP response splitting attacks via vectors involving the url variable.

Affected Packages

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`moodle/moodle`	all versions	1.9.15`composer require moodle/moodle:^1.9.15`
🐘Packagist	`moodle/moodle`	≥ 2.0&&< 2.0.6	2.0.6`composer require moodle/moodle:^2.0.6`
🐘Packagist	`moodle/moodle`	≥ 2.1&&< 2.1.3	2.1.3`composer require moodle/moodle:^2.1.3`

Affected Products

1 product · 24 configurations

Application

moodlemoodle

24 versions

1.9.11.9.21.9.31.9.41.9.51.9.61.9.71.9.81.9.91.9.101.9.111.9.12

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

CRLF injection vulnerability in calendar/set.php in the Calendar compone…

penturalabs.wordpress.comNVDDec 2020

Detection & mitigation playbook

Open-source dependency

Detect
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 1.9.15 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2011-4203 is resolved across your whole dependency graph.
Workarounds
Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.

Frequently Asked Questions

O3 Security · Impact-Aware SCA

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