CVE-2014-9668 in FreeType
Summary
by MITRE
The woff_open_font function in sfnt/sfobjs.c in FreeType before 2.5.4 proceeds with offset+length calculations without restricting length values, which allows remote attackers to cause a denial of service (integer overflow and heap-based buffer overflow) or possibly have unspecified other impact via a crafted Web Open Font Format (WOFF) file.
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Analysis
by VulDB Data Team • 03/08/2022
The vulnerability identified as CVE-2014-9668 represents a critical security flaw in the FreeType font rendering library, specifically within the woff_open_font function located in sfnt/sfobjs.c. This issue affects FreeType versions prior to 2.5.4 and demonstrates a classic case of insufficient input validation that can lead to severe operational consequences. The flaw occurs when the function processes offset and length calculations without proper restrictions on length values, creating an environment where maliciously crafted Web Open Font Format files can trigger unpredictable behavior in applications that utilize FreeType for font processing.
The technical implementation of this vulnerability stems from improper handling of integer arithmetic within the font parsing logic. When a WOFF file is processed, the function calculates memory allocation based on offset and length parameters that are directly derived from the font file's metadata. Without adequate bounds checking or length validation, attackers can craft WOFF files containing maliciously large length values that, when processed, result in integer overflow conditions. This overflow can cause the system to allocate insufficient memory or attempt to allocate memory inappropriately sized for the actual data, leading to heap-based buffer overflows that can corrupt adjacent memory regions.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to potentially enable more sophisticated attack vectors. While the primary effect manifests as denial of service through integer overflow and heap-based buffer overflow conditions, the unspecified other impacts referenced in the CVE description suggest that under certain circumstances, this vulnerability could be exploited to execute arbitrary code or escalate privileges. The vulnerability affects any application that relies on FreeType for font rendering, including web browsers, document viewers, and operating system components that process font files. This broad attack surface makes the vulnerability particularly dangerous as it can be exploited through multiple entry points, potentially allowing remote attackers to compromise systems simply by enticing users to view maliciously crafted web content or documents containing the malicious font files.
The vulnerability aligns with CWE-190, which specifically addresses integer overflow and underflow conditions, and demonstrates how improper integer handling can lead to memory corruption vulnerabilities. From an ATT&CK framework perspective, this vulnerability maps to the T1203 - Exploitation for Client Execution tactic, where attackers leverage application vulnerabilities to execute malicious code. The exploitation requires minimal user interaction, typically involving the automatic processing of font files through applications that utilize FreeType, making it particularly concerning for web browsers and other applications that automatically render font content.
Mitigation strategies for CVE-2014-9668 primarily focus on updating to FreeType version 2.5.4 or later, where the vulnerability has been patched through proper input validation and bounds checking mechanisms. Organizations should prioritize patch management across all systems that utilize FreeType for font processing, including web browsers, document processing applications, and operating system components. Additional defensive measures include implementing sandboxing techniques for font processing, restricting font file types that can be processed, and deploying network-based intrusion detection systems that can identify and block malicious WOFF files. Security monitoring should specifically focus on detecting unusual font processing patterns that might indicate exploitation attempts, particularly in environments where users are not expected to process arbitrary font files from untrusted sources.