CVE-2014-9666 in FreeType
Summary
by MITRE
The tt_sbit_decoder_init function in sfnt/ttsbit.c in FreeType before 2.5.4 proceeds with a count-to-size association without restricting the count value, which allows remote attackers to cause a denial of service (integer overflow and out-of-bounds read) or possibly have unspecified other impact via a crafted embedded bitmap.
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Analysis
by VulDB Data Team • 03/08/2022
The vulnerability described in CVE-2014-9666 affects the FreeType font rendering library, specifically within the tt_sbit_decoder_init function located in sfnt/ttsbit.c. This flaw exists in FreeType versions prior to 2.5.4 and represents a critical security issue that can be exploited remotely. The vulnerability stems from improper validation of count values during the processing of embedded bitmap data within TrueType fonts, creating a scenario where maliciously crafted font files can trigger unexpected behavior in applications that utilize FreeType for font rendering.
The technical implementation of this vulnerability involves an integer overflow condition that occurs when the function processes the count-to-size association for embedded bitmap data. When a crafted font file contains malformed count values, the tt_sbit_decoder_init function fails to properly validate these values before using them in memory allocation calculations. This lack of input sanitization allows the count parameter to exceed acceptable bounds, leading to integer overflow conditions that subsequently cause out-of-bounds memory reads. The vulnerability operates at the intersection of software robustness and memory safety, where the absence of proper boundary checking enables attackers to manipulate the execution flow of font rendering processes.
The operational impact of CVE-2014-9666 extends beyond simple denial of service conditions to potentially enable more severe consequences including arbitrary code execution or information disclosure. When applications process maliciously crafted font files, the integer overflow can result in memory corruption that may be exploitable by attackers to execute arbitrary code within the context of the vulnerable application. This vulnerability affects a wide range of systems since FreeType is widely used across operating systems, web browsers, and applications for font rendering. The remote exploitation capability means that attackers can deliver malicious font files through various channels including email attachments, web pages, or file sharing platforms, making this vulnerability particularly dangerous in real-world scenarios.
From a cybersecurity perspective, this vulnerability aligns with CWE-190, which specifically addresses integer overflow conditions, and demonstrates the importance of proper input validation in security-critical software components. The ATT&CK framework categorizes this as a vulnerability exploitation technique that leverages software flaws to achieve remote code execution or denial of service. The vulnerability's classification as a remote attack vector means it can be exploited without requiring local access, making it particularly concerning for web-based applications that process untrusted font data. Organizations using FreeType in their applications should prioritize immediate patching to address this vulnerability, as the potential for exploitation extends across multiple attack surfaces including web browsers, document viewers, and other font rendering applications.
Mitigation strategies for CVE-2014-9666 require immediate deployment of FreeType version 2.5.4 or later, which includes proper bounds checking and input validation for embedded bitmap count values. Additionally, system administrators should implement application whitelisting policies to restrict font file processing to trusted sources and consider deploying web application firewalls that can detect and block malicious font file content. The vulnerability also underscores the importance of regular security updates and vulnerability management processes, as this flaw existed for several years before proper mitigation was implemented. Organizations should conduct comprehensive vulnerability assessments to identify all systems utilizing FreeType and ensure that appropriate security controls are in place to prevent exploitation of this and similar font rendering vulnerabilities.