CVE-2019-1109 in Office
Summary
by MITRE
A spoofing vulnerability exists when Microsoft Office Javascript does not check the validity of the web page making a request to Office documents.An attacker who successfully exploited this vulnerability could read or write information in Office documents.The security update addresses the vulnerability by correcting the way that Microsoft Office Javascript verifies trusted web pages., aka 'Microsoft Office Spoofing Vulnerability'.
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Analysis
by VulDB Data Team • 07/09/2020
This vulnerability represents a critical spoofing weakness in Microsoft Office's JavaScript implementation that undermines the security boundaries between trusted and untrusted web content. The flaw occurs when Office documents attempt to make web requests through JavaScript, failing to properly validate the originating web page's authenticity and trustworthiness. This represents a fundamental breakdown in the security model that Microsoft Office employs to protect users from malicious web interactions within document contexts. The vulnerability specifically affects the verification mechanisms that should ensure only legitimate and trusted web sources can interact with Office documents through JavaScript APIs.
The technical implementation flaw stems from insufficient validation of web request origins within Office's JavaScript runtime environment. When documents contain embedded JavaScript code that attempts to communicate with external web resources, the system should verify that these requests originate from trusted domains or sources. However, this validation process fails to properly authenticate the requesting web page, allowing malicious actors to craft deceptive web pages that appear legitimate to Office's security checks. This weakness creates a path for attackers to manipulate how Office documents interact with web resources, effectively bypassing the intended security controls.
The operational impact of this vulnerability is significant as it allows attackers to perform unauthorized read and write operations on Office documents. An attacker who successfully exploits this vulnerability could access sensitive data within documents, modify document content, or potentially exfiltrate information without proper authorization. The attack surface extends beyond simple document manipulation to include potential data theft, document corruption, and the possibility of using compromised documents as a vector for further attacks. This vulnerability particularly affects users who open documents from untrusted sources or when documents contain embedded web content that triggers malicious JavaScript behavior.
Microsoft addressed this vulnerability through a security update that enhances the validation mechanisms within Office's JavaScript implementation. The fix strengthens the verification process to ensure that web requests originating from Office documents properly authenticate the requesting web page's legitimacy before allowing any data exchange or modification operations. This update aligns with security best practices for preventing cross-site request forgery and spoofing attacks by implementing proper origin validation and authentication checks. Organizations should prioritize applying this update to protect against exploitation attempts and maintain the integrity of Office document environments.
This vulnerability maps to CWE-346, which specifically addresses "Improper Verification of Source of a Communication Channel" and relates to the broader category of spoofing attacks. The attack pattern aligns with techniques described in the MITRE ATT&CK framework under T1190 - "Exploit Public-Facing Application" and T1211 - "Exploitation for Defense Evasion", as attackers can leverage this weakness to gain unauthorized access to document contents and potentially evade detection mechanisms. The vulnerability demonstrates the importance of proper input validation and source authentication in web-based document processing environments where multiple security contexts intersect.