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MoodleCMS

CVE-2011-4586

MEDIUM · 5.0 CVSS v2.0 Published 2012-07-20
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
59/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
CRLF injection vulnerability in calendar/set.php in the Calendar subsystem in Moodle 1.9.x before 1.9.15, 2.0.x before 2.0.6, and 2.1.x before 2.1.3 allows remote attackers to inject arbitrary HTTP headers and conduct HTTP response splitting attacks via unspecified vectors.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

CRLF injection vulnerability in Moodle's calendar/set.php allows attackers to inject arbitrary HTTP headers by inserting carriage return (\r) and line feed (\n) characters into user-supplied input. This enables HTTP response splitting attacks where malicious headers can be injected into responses, potentially leading to cache poisoning, session hijacking, or cross-site scripting.

MitigationUpgrade to Moodle 1.9.15, 2.0.6, or 2.1.3 or later which contain the fix. As a compensating control, implement input validation to reject or sanitize CRLF characters in HTTP header fields.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
MoodleCMS
Affected:= 1.9.1= 1.9.2= 1.9.3= 1.9.4= 1.9.5= 1.9.6= 1.9.7= 1.9.8= 1.9.9= 1.9.10= 1.9.11= 1.9.12

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Authentication
None
Confidentiality
None
Integrity
Partial
Availability
None

AV:N/AC:L/Au:N/C:N/I:P/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check Moodle version
    Locate version.php in your Moodle root directory and read the $release or $version variable to determine the installed version
    Affected if The installed version is 1.9.1, 1.9.2, 1.9.3, 1.9.4, 1.9.5, 1.9.6, 1.9.7, 1.9.8, 1.9.9, 1.9.10, 1.9.11, or 1.9.12
  2. Verify calendar/set.php exists
    Check if the file calendar/set.php exists in your Moodle installation directory
    Affected if The file calendar/set.php is present in the Moodle installation
  3. Confirm calendar module is enabled
    Log in as administrator and navigate to Site Administration > Plugins > Activity modules > Calendar, or check the mdl_modules table in the database for the calendar module record with visible=1
    Affected if The calendar module is enabled and accessible to users

You are likely affected if your Moodle version is 1.9.1 through 1.9.12 and the calendar/set.php file exists with the calendar module enabled.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to Moodle 1.9.15, 2.0.6, or 2.1.3 or later which contain the fix. As a compensating control, implement input validation to reject or sanitize CRLF characters in HTTP header fields.

Fix this in Moodle Scoped from the published advisory
  • Consultation4.0 h
  • Implementation3.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,150
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Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2011-4586 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data