CVE-2013-0304 in ownCloud
Summary
by MITRE
ownCloud Server before 4.5.7 does not properly check ownership of calendars, which allows remote authenticated users to read arbitrary calendars via the calid parameter to /apps/calendar/export.php. NOTE: this issue has been reported as a cross-site request forgery (CSRF) vulnerability, but due to lack of details, it is uncertain what the root cause is.
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Analysis
by VulDB Data Team • 03/31/2025
The vulnerability identified as CVE-2013-0304 affects ownCloud Server versions prior to 4.5.7 and represents a critical access control flaw that undermines the integrity of calendar data protection mechanisms. This issue manifests through improper ownership validation during calendar operations, specifically within the calendar export functionality that processes requests through the /apps/calendar/export.php endpoint. The vulnerability enables authenticated attackers to exploit the calid parameter to access calendar data belonging to other users, effectively bypassing the intended authorization controls that should prevent such cross-user data access.
The technical root cause of this vulnerability stems from insufficient input validation and access control checks within the calendar management system. When a user requests calendar export functionality, the application fails to properly verify whether the requesting user has legitimate authorization to access the specified calendar resource. This misconfiguration allows attackers to manipulate the calid parameter to reference calendars owned by other users, thereby gaining unauthorized access to sensitive calendar information including event details, meeting schedules, and personal appointments. The flaw operates at the application logic level where proper authentication and authorization checks are bypassed, creating a path for privilege escalation through data exposure.
From an operational impact perspective, this vulnerability poses significant risks to user privacy and organizational security. Attackers can exploit this weakness to gather sensitive personal and professional information from calendar entries, potentially enabling social engineering attacks, phishing campaigns, or corporate espionage. The vulnerability affects any authenticated user within the ownCloud environment, making it particularly dangerous in organizational settings where calendar data contains confidential business information, strategic meeting schedules, and personal details. The exposure of calendar data can lead to reputation damage, regulatory compliance violations, and potential legal consequences depending on the jurisdiction and data protection requirements in place.
The vulnerability aligns with CWE-285, which addresses improper authorization issues in software systems, and demonstrates characteristics consistent with privilege escalation through data access control bypass. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and credential access, as attackers can leverage the flaw to gain unauthorized access to resources they should not be able to view. The issue also reflects poor input validation practices that can be categorized under ATT&CK's data manipulation and reconnaissance activities. Organizations using vulnerable versions of ownCloud should prioritize immediate remediation through patching to version 4.5.7 or later, while implementing additional monitoring for suspicious calendar access patterns and access control violations.
Mitigation strategies should include immediate patch deployment to upgrade to the affected software version 4.5.7 or later, which contains the necessary fixes for the calendar ownership validation logic. Organizations should also implement additional access control measures such as rate limiting on calendar export requests, enhanced logging of calendar access patterns, and regular security audits of calendar data access controls. Network segmentation and monitoring solutions should be deployed to detect unusual calendar access patterns that may indicate exploitation attempts. Security teams should conduct comprehensive vulnerability assessments to identify similar access control flaws in other applications within the environment and establish proper incident response procedures for handling potential calendar data exposure incidents.