CVE-2016-5740 in OX AppSuite
Summary
by MITRE
An issue was discovered in Open-Xchange OX App Suite before 7.8.2-rev5. JavaScript code can be used as part of ical attachments within scheduling E-Mails. This content, for example an appointment's location, will be presented to the user at the E-Mail App, depending on the invitation workflow. This code gets executed within the context of the user's current session. Malicious script code can be executed within a user's context. This can lead to session hijacking or triggering unwanted actions via the web interface (sending mail, deleting data etc.).
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Analysis
by VulDB Data Team • 12/07/2024
The vulnerability identified as CVE-2016-5740 represents a critical cross-site scripting flaw within the Open-Xchange OX App Suite email client software. This security issue affects versions prior to 7.8.2-rev5 and stems from the improper handling of iCalendar attachments within scheduling emails. The vulnerability occurs when JavaScript code embedded within iCal attachments is processed and executed within the user's browser context during email viewing operations. This flaw falls under the CWE-79 category of Cross-Site Scripting, specifically representing a server-side code injection vulnerability that allows malicious actors to inject executable code into email content.
The technical exploitation of this vulnerability occurs through the scheduling workflow of the email application where iCalendar attachments containing malicious JavaScript are embedded within appointment invitations. When users view these emails, the JavaScript code executes within the security context of their active session, leveraging the trust relationship between the user and the email application. This execution context provides attackers with the ability to perform actions that are normally restricted to the authenticated user, effectively bypassing typical session security controls. The vulnerability demonstrates a classic case of insufficient input validation and output encoding, where user-supplied data from iCalendar attachments is not properly sanitized before being rendered in the email interface.
The operational impact of this vulnerability extends beyond simple script execution to encompass full session compromise and potential data exfiltration. Attackers can leverage this vulnerability to hijack user sessions, gaining unauthorized access to sensitive email content, calendar data, and personal information stored within the OX App Suite environment. The malicious code execution can trigger unwanted actions such as sending unauthorized emails, deleting calendar entries, modifying user preferences, or even establishing persistent backdoors within the user's session. This vulnerability particularly affects organizations relying on the OX App Suite for business email services, as it can be exploited through simple email phishing campaigns without requiring complex attack vectors or privileged access to the email infrastructure.
Mitigation strategies for CVE-2016-5740 primarily focus on updating to the patched version 7.8.2-rev5 or later, which implements proper input sanitization and output encoding for iCalendar attachments. Organizations should also implement additional security controls such as email filtering rules that block suspicious iCalendar attachments, network-level restrictions on calendar data processing, and user education regarding the dangers of opening unsolicited email attachments. The ATT&CK framework categorizes this vulnerability under T1059.007 for Scripting and T1566 for Phishing, highlighting the social engineering aspects of exploitation combined with technical code execution. Security teams should also consider implementing content security policies that restrict script execution within email rendering contexts and monitor for unusual email attachment patterns that might indicate attempted exploitation of this vulnerability.