CVE-2010-3324 in SharePoint Server
Summary
by MITRE
The toStaticHTML function in Microsoft Internet Explorer 8, and the SafeHTML function in Microsoft Windows SharePoint Services 3.0 SP2, SharePoint Foundation 2010, Office SharePoint Server 2007 SP2, Groove Server 2010, and Office Web Apps, allows remote attackers to bypass the cross-site scripting (XSS) protection mechanism and conduct XSS attacks via a crafted use of the Cascading Style Sheets (CSS) @import rule, aka "HTML Sanitization Vulnerability," a different vulnerability than CVE-2010-1257.
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Analysis
by VulDB Data Team • 09/25/2021
The vulnerability described in CVE-2010-3324 represents a critical weakness in Microsoft's HTML sanitization mechanisms that affected Internet Explorer 8 and various SharePoint products. This flaw specifically targets the toStaticHTML function in Internet Explorer and the SafeHTML function in SharePoint services, both of which were designed to prevent cross-site scripting attacks by filtering potentially dangerous HTML content. The vulnerability operates through a sophisticated bypass technique that exploits the CSS @import rule to circumvent the intended security protections, allowing attackers to inject malicious scripts that would normally be blocked by the sanitization process. This represents a significant failure in the security model that Microsoft had implemented to protect users from XSS attacks, which are among the most common and dangerous web application vulnerabilities.
The technical implementation of this vulnerability involves the manipulation of CSS import directives within HTML content to create a bypass condition that allows malicious code to pass through the sanitization filters. When Internet Explorer processes HTML content through the toStaticHTML function or when SharePoint processes content through the SafeHTML function, the CSS import rule can be crafted in such a way that it appears harmless to the sanitization engine while actually enabling the execution of malicious scripts. This technique exploits the complex interaction between CSS parsing and HTML sanitization, where the security filters fail to properly account for the dynamic nature of CSS import statements and their potential to reference external content that can contain malicious payloads. The vulnerability specifically affects the order of operations in the sanitization process, where CSS processing occurs before proper HTML validation, allowing attackers to craft content that initially passes security checks but ultimately executes harmful code when rendered in the browser.
The operational impact of this vulnerability is severe and far-reaching across Microsoft's ecosystem, particularly affecting organizations that rely heavily on SharePoint services for collaboration and content management. Attackers could leverage this vulnerability to execute arbitrary JavaScript code in the context of a user's session, potentially leading to session hijacking, data theft, privilege escalation, or complete system compromise. The vulnerability's persistence across multiple Microsoft products including SharePoint Foundation 2010, Office SharePoint Server 2007 SP2, Groove Server 2010, and Office Web Apps demonstrates the widespread nature of the issue and the potential for large-scale exploitation. Organizations using these platforms faced significant risk of unauthorized access and data breaches, as the vulnerability could be exploited through various attack vectors including email attachments, web-based content submissions, or compromised web pages that users would visit. The attack could be particularly effective in enterprise environments where SharePoint is used for document sharing and collaboration, as users might be tricked into viewing maliciously crafted content that appears legitimate.
Mitigation strategies for this vulnerability required immediate patching of affected Microsoft products, with Microsoft releasing security updates to address the sanitization flaw in both Internet Explorer and SharePoint services. Organizations needed to ensure their SharePoint installations were updated to the latest service packs and security patches, while also implementing additional defensive measures such as enhanced web application firewalls, stricter content filtering policies, and user education programs to reduce the risk of successful exploitation. The vulnerability highlights the importance of comprehensive security testing for sanitization functions and demonstrates how seemingly benign features like CSS processing can introduce critical security weaknesses. From a cybersecurity perspective, this vulnerability aligns with CWE-79 (Cross-site Scripting) and represents a specific implementation flaw that could be categorized under ATT&CK technique T1203 (Exploitation for Client Execution) and T1566 (Phishing). Organizations should have implemented layered security approaches including regular security assessments of web application sanitization mechanisms, proper input validation, and monitoring for unusual content patterns that might indicate exploitation attempts. The incident underscored the critical need for security professionals to understand how different web technologies interact and potentially create unexpected security vulnerabilities.