CVE-2020-17006 in Dynamics CRM
Summary
by MITRE • 11/11/2020
Microsoft Dynamics 365 (on-premises) Cross-site Scripting Vulnerability This CVE ID is unique from CVE-2020-17005, CVE-2020-17018, CVE-2020-17021.
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Analysis
by VulDB Data Team • 12/04/2020
Microsoft Dynamics 365 on-premises installations contain a cross-site scripting vulnerability that allows authenticated users to execute malicious scripts within the context of other users' sessions. This vulnerability specifically affects the web-based interfaces of the on-premises deployment model, creating a persistent threat vector that can be exploited by attackers who have already gained access to legitimate user credentials. The flaw resides in how the application processes and renders user-supplied input within web pages, failing to properly sanitize or escape potentially malicious content before displaying it to end users. This vulnerability is particularly concerning as it operates within the trusted environment of legitimate users, making detection and prevention significantly more challenging.
The technical implementation of this XSS vulnerability stems from inadequate input validation mechanisms within the Dynamics 365 web application framework. When users interact with various administrative and operational interfaces, the system fails to adequately filter or encode special characters that could be used to inject malicious script code. This weakness allows attackers to craft specially formatted inputs that, when processed by the application, get executed in the browser context of other users who view the affected pages. The vulnerability is classified as a persistent XSS attack vector, meaning that malicious payloads can be stored within the application's database and executed whenever affected pages are accessed, creating a long-term threat that can impact multiple users over extended periods. This flaw aligns with CWE-79 which defines cross-site scripting as the failure to properly escape output content, and represents a classic example of how web applications can become attack vectors for themselves.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to escalate privileges, steal session cookies, perform unauthorized transactions, and potentially gain access to sensitive business data. An attacker with low-privilege access can leverage this vulnerability to impersonate higher-privileged users, effectively bypassing access controls and gaining unauthorized access to critical business information. The attack surface is particularly wide given that Dynamics 365 applications typically handle sensitive customer data, financial records, and operational workflows that make them attractive targets for cybercriminals. The vulnerability can be exploited through various attack vectors including email attachments, web forms, and direct URL manipulation, making it difficult to defend against completely without comprehensive security controls. This vulnerability also maps to several ATT&CK techniques including T1531 for credential access through session hijacking and T1059 for command and control through script injection.
Mitigation strategies for this vulnerability should include immediate application of Microsoft security patches, implementation of robust input validation controls, and deployment of web application firewalls to monitor and filter malicious traffic. Organizations should also implement proper security monitoring to detect unusual patterns of user behavior that might indicate exploitation attempts. The recommended approach includes enabling Content Security Policy headers, implementing proper output encoding for all user-supplied data, and conducting regular security assessments of the application's web interfaces. Additionally, network segmentation and privilege-based access controls should be enforced to limit the potential damage from successful exploitation attempts. Regular security training for administrators and users can help identify potential social engineering attempts that might be used to gain initial access to the system, while comprehensive logging and audit trails should be maintained to facilitate forensic analysis in case of successful attacks. Organizations should also consider implementing multi-factor authentication to add additional layers of protection beyond simple credential theft.