CVE-2015-1671 in Windows
Summary
by MITRE
The Windows DirectWrite library, as used in Microsoft .NET Framework 3.0 SP2, 3.5, 3.5.1, 4, 4.5, 4.5.1, and 4.5.2; Office 2007 SP3 and 2010 SP2; Live Meeting 2007 Console; Lync 2010; Lync 2010 Attendee; Lync 2013 SP1; Lync Basic 2013 SP1; Silverlight 5 before 5.1.40416.00; and Silverlight 5 Developer Runtime before 5.1.40416.00, allows remote attackers to execute arbitrary code via a crafted TrueType font, aka "TrueType Font Parsing Vulnerability."
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Analysis
by VulDB Data Team • 04/22/2026
The vulnerability identified as CVE-2015-1671 represents a critical security flaw within the Windows DirectWrite rendering library that affects multiple Microsoft products and frameworks. This vulnerability specifically targets the parsing mechanism of TrueType font files, which are commonly used for text rendering in applications and operating systems. The flaw exists in how DirectWrite handles malformed or specially crafted TrueType font data during the rendering process, creating an exploitable condition that can be leveraged by remote attackers to execute arbitrary code on affected systems. The vulnerability impacts a wide range of Microsoft products including various versions of the .NET Framework, Office suites, Lync communications platforms, and Silverlight runtime environments, making it particularly dangerous due to its widespread presence across enterprise and consumer deployments. The vulnerability is classified under CWE-125 as an out-of-bounds read, which occurs when the DirectWrite library attempts to access memory locations beyond the bounds of allocated buffers during font parsing operations.
The technical exploitation of this vulnerability involves crafting a malicious TrueType font file that, when processed by the affected DirectWrite library, triggers a buffer overflow or memory corruption condition. When an application or system renders text using the compromised font file, the DirectWrite library's parsing routine fails to properly validate font structure data, leading to memory corruption that can be exploited to overwrite critical memory locations. Attackers can leverage this condition to inject and execute malicious code with the privileges of the affected application, typically resulting in system compromise. The attack vector is particularly concerning because TrueType fonts are frequently encountered in legitimate document processing, web browsing, and email rendering scenarios, making the attack surface extremely broad. The vulnerability aligns with ATT&CK technique T1203 (Exploitation for Client Execution) and T1059 (Command and Scripting Interpreter) as it enables attackers to execute arbitrary code through legitimate system components and can be used to establish persistent access through command execution capabilities.
The operational impact of CVE-2015-1671 extends beyond individual system compromise to affect entire enterprise environments where Microsoft products are widely deployed. Organizations running affected versions of .NET Framework, Office, or Lync software face significant risk of unauthorized access, data exfiltration, and system takeover when users encounter maliciously crafted documents or web content containing the vulnerable font files. The vulnerability's presence in Silverlight runtime environments particularly affects web applications that utilize rich media content, while its inclusion in Office products means that email attachments and document files can serve as attack vectors. The widespread adoption of affected software across different Microsoft products creates a cascading risk where compromise of one application can potentially lead to broader system infiltration. Security teams must consider the implications of this vulnerability in their incident response planning, as the exploitation can occur through multiple vectors including phishing emails, malicious websites, or compromised documents. The vulnerability's remediation requires patching of affected Microsoft products and frameworks, with particular attention to ensuring all endpoints running Silverlight, Office, or Lync applications are properly updated.
Organizations should implement comprehensive mitigation strategies that include immediate patch deployment across all affected Microsoft products, along with network monitoring for suspicious font-related file transfers and execution patterns. Security controls should focus on restricting font processing capabilities in email gateways and web browsers where possible, while maintaining awareness of the ATT&CK framework's T1203 and T1059 techniques that leverage such vulnerabilities. The vulnerability demonstrates the critical importance of font validation in system security, as font rendering libraries often receive minimal security scrutiny despite their fundamental role in system operation. Regular security assessments should include verification of font handling components in all applications, particularly those that process untrusted content. The remediation process requires careful coordination between IT teams and security operations to ensure all affected systems are properly updated, while also implementing additional protective measures such as application whitelisting and privilege separation to limit potential damage from successful exploitation attempts.