CVE-2016-6851 in OX Guard
Summary
by MITRE
An issue was discovered in Open-Xchange OX Guard before 2.4.2-rev5. Script code can be provided as parameter to the OX Guard guest reader web application. This allows cross-site scripting attacks against arbitrary users since no prior authentication is needed. 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.) in case the user has an active session on the same domain already.
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Analysis
by VulDB Data Team • 12/08/2024
The vulnerability identified as CVE-2016-6851 represents a critical cross-site scripting flaw in Open-Xchange OX Guard versions prior to 2.4.2-rev5. This security weakness stems from the guest reader web application's improper handling of user-supplied script code within URL parameters, creating an avenue for malicious actors to inject and execute arbitrary JavaScript code against unsuspecting users. The flaw operates without requiring any authentication prerequisites, making it particularly dangerous as it can be exploited by attackers who simply need to entice victims to click on malicious links. The vulnerability directly maps to CWE-79 which defines cross-site scripting as a common web application security flaw where untrusted data is incorporated into web pages without proper validation or encoding.
The technical implementation of this vulnerability allows attackers to craft malicious URLs containing script payloads that get executed within the victim's browser context when the guest reader application processes these parameters. Since the application does not perform adequate input sanitization or output encoding, any script code passed through the URL parameters is directly rendered and executed by the browser. This creates a persistent threat where the malicious code can operate within the same security context as the legitimate user, effectively enabling session hijacking attacks. The compromised user session can then be leveraged to perform unauthorized actions such as sending emails, deleting data, or accessing sensitive information through the web interface, all while maintaining the victim's authenticated state.
The operational impact of this vulnerability extends beyond simple script execution as it represents a complete breakdown in the application's security model for guest users. Attackers can exploit this flaw to create a wide range of malicious scenarios including credential theft, data exfiltration, and privilege escalation through session manipulation. The vulnerability's effectiveness is amplified by the fact that it requires no authentication, meaning that even unauthenticated users can potentially compromise authenticated sessions of other users who happen to be logged into the same domain. This makes it particularly dangerous in enterprise environments where users maintain active sessions for extended periods, creating a window of opportunity for exploitation. The attack vector aligns with ATT&CK technique T1059.007 which describes the use of script-based commands to execute malicious code in the context of the victim's session.
Organizations affected by this vulnerability should immediately implement mitigation strategies including patching to version 2.4.2-rev5 or later, which addresses the input validation issues. Additionally, implementing proper input sanitization measures such as parameter validation and output encoding can prevent similar vulnerabilities from occurring in other applications. Network-level protections such as web application firewalls should be configured to detect and block suspicious script code patterns in URL parameters. Regular security assessments and penetration testing should be conducted to identify similar input validation flaws in other web applications within the organization's infrastructure. The vulnerability serves as a reminder of the critical importance of validating all user inputs and implementing proper security controls even in guest or unauthenticated access points of web applications.