CVE-2013-6997 in AppSuite
Summary
by MITRE
Multiple cross-site scripting (XSS) vulnerabilities in Open-Xchange (OX) AppSuite 7.4.0 and earlier allow remote attackers to inject arbitrary web script or HTML via (1) an HTML email with crafted CSS code containing wildcards or (2) office documents containing "crafted hyperlinks with script URL handlers."
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Analysis
by VulDB Data Team • 06/09/2021
The vulnerability CVE-2013-6997 represents a critical cross-site scripting flaw affecting Open-Xchange AppSuite versions 7.4.0 and earlier, demonstrating the persistent risks associated with email client security in enterprise environments. This vulnerability operates through two distinct attack vectors that exploit the application's handling of rich content, specifically targeting the rendering of HTML emails and office documents. The first vector involves HTML emails containing crafted CSS code with wildcard characters that can bypass security filters, while the second vector exploits office documents with hyperlinks that utilize script URL handlers to execute malicious code.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding within the Open-Xchange email processing pipeline. When the application processes HTML emails containing crafted CSS code with wildcards, it fails to properly sanitize the content before rendering it in the user's browser context. Similarly, when office documents containing hyperlinks with script URL handlers are processed, the application does not adequately validate or escape these URL schemes that could trigger JavaScript execution. This represents a classic XSS vulnerability categorized under CWE-79, which specifically addresses Cross-Site Scripting flaws in web applications where user-controllable data is not properly sanitized before being rendered in web pages.
The operational impact of CVE-2013-6997 extends beyond simple script injection, creating potential pathways for more sophisticated attacks within enterprise networks. Attackers leveraging this vulnerability could execute malicious scripts in the context of authenticated users' browsers, potentially leading to session hijacking, data exfiltration, or privilege escalation within the email environment. The vulnerability particularly affects organizations using Open-Xchange AppSuite as their primary email infrastructure, where the attack surface includes all users who process emails or office documents containing malicious content. This creates a significant risk for corporate email systems where users may inadvertently open compromised emails or documents, especially in environments with less security awareness training.
Organizations should implement comprehensive mitigation strategies that address both the immediate vulnerability and underlying security gaps in their email processing infrastructure. The primary remediation involves upgrading to Open-Xchange AppSuite versions that contain proper input validation and output encoding mechanisms, effectively preventing the execution of malicious scripts through crafted CSS code or script URL handlers. Additionally, implementing strict email filtering policies, content security policies, and user education programs can significantly reduce the risk of successful exploitation. Security controls should also include monitoring for suspicious email patterns and implementing web application firewalls that can detect and block malicious payloads before they reach end users. The vulnerability's classification under ATT&CK technique T1566 highlights its potential for initial access through spearphishing campaigns, making it particularly dangerous in targeted attack scenarios where adversaries seek to establish persistent access through email-based vectors. Organizations should also consider implementing email encryption and digital signatures to provide additional layers of protection against content manipulation attacks that could exploit similar vulnerabilities in the future.