CVE-2011-4586: CRLF injection vulnerability in calendar/set.php in the Calendar subsystem in Moodle 1.9.x before 1.9.15, 2...

Security readout for executives and security teams

This issue affects old Moodle calendar code and could let a remote attacker make the server send extra HTTP headers. That can support response-splitting style attacks, potentially confusing browsers, caches, or downstream security controls. Exposure is most likely on legacy Moodle sites that still run the named vulnerable branches and expose the calendar subsystem to remote users. Prioritize if any internet-facing legacy Moodle instance remains in production. This is old, but old LMS systems often persist and may expose student, staff, or customer workflows. Mitigation focus: Upgrade affected Moodle versions to at least 1.9.15, 2.0.6, or 2.1.3.; Prefer migrating to a currently supported Moodle release where operationally possible.; Review Moodle and Debian advisories for package-specific update guidance..

Prepared

Jun 24, 2026, 12:34 UTC (UTC+00:00)

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.