CVE-2017-8728 in Windows
Summary
by MITRE
Microsoft Windows PDF Library in Microsoft Windows 8.1 and Windows RT 8.1, Windows Server 2012 and R2, Windows 10 Gold, 1511, 1607, 1703, and Windows Server 2016 allows an attacker to execute arbitrary code in the context of the current user, due to the way that Windows PDF Library handles objects in memory, aka "Windows PDF Remote Code Execution Vulnerability". This CVE ID is unique from CVE-2017-8737.
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Analysis
by VulDB Data Team • 01/12/2021
The vulnerability identified as CVE-2017-8728 represents a critical remote code execution flaw within the Microsoft Windows PDF Library component that affects multiple Windows operating systems including Windows 8.1, Windows RT 8.1, Windows Server 2012 and R2, Windows 10 versions 1511, 1607, 1703, and Windows Server 2016. This vulnerability stems from improper handling of objects in memory by the PDF library implementation, creating a pathway for attackers to execute arbitrary code with the privileges of the currently logged-in user. The flaw specifically manifests when the Windows PDF Library processes malformed PDF files, particularly those containing specially crafted objects that trigger memory corruption during parsing operations.
The technical root cause of this vulnerability aligns with CWE-125, which describes out-of-bounds read conditions, and CWE-787, which covers out-of-bounds write vulnerabilities. The Windows PDF Library fails to properly validate and sanitize input objects within PDF files, allowing attackers to manipulate memory structures through carefully constructed malicious documents. When a user opens a crafted PDF file, the library's parsing routine encounters these malformed objects and attempts to process them without adequate bounds checking, resulting in memory corruption that can be exploited to redirect program execution flow. This memory corruption typically occurs during the handling of embedded objects, streams, or complex graphical elements within the PDF structure.
From an operational perspective, this vulnerability presents significant risk as it requires no privileged access to exploit and can be delivered through standard user interactions such as opening a malicious PDF document. The attack surface is extensive given that PDF viewing is a common user activity across all supported platforms, making this vulnerability particularly dangerous in enterprise environments where users frequently open documents from untrusted sources. The remote code execution capability allows attackers to install malware, modify system files, establish persistence mechanisms, or escalate privileges depending on the user context. The vulnerability's classification as a remote code execution flaw means that successful exploitation could lead to complete system compromise without requiring local access or administrative privileges.
Mitigation strategies for CVE-2017-8728 should focus on immediate patch deployment through Microsoft's regular security updates, as the vendor released patches in August 2017 as part of their security bulletin. Organizations should implement additional protective measures including PDF file scanning and filtering at network perimeters, disabling automatic PDF opening in web browsers, and implementing application whitelisting controls to restrict execution of untrusted PDF processing applications. Network segmentation and monitoring for suspicious PDF file downloads or opening activities can help detect potential exploitation attempts. Security teams should also consider deploying exploit prevention technologies and ensuring that all systems are kept up-to-date with the latest security patches. The vulnerability demonstrates the importance of proper input validation and memory management practices, aligning with ATT&CK technique T1203 for exploitation of remote services and T1059 for command and scripting interpreter usage during post-exploitation activities. Organizations should also conduct security awareness training to reduce the likelihood of users inadvertently opening malicious PDF documents, as social engineering remains a primary delivery method for such exploits.