CVE-2014-9665 in FreeType
Summary
by MITRE
The Load_SBit_Png function in sfnt/pngshim.c in FreeType before 2.5.4 does not restrict the rows and pitch values of PNG data, which allows remote attackers to cause a denial of service (integer overflow and heap-based buffer overflow) or possibly have unspecified other impact by embedding a PNG file in a .ttf font file.
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Analysis
by VulDB Data Team • 03/08/2022
The vulnerability identified as CVE-2014-9665 resides within the FreeType font rendering library, specifically in the Load_SBit_Png function located in sfnt/pngshim.c. This flaw affects FreeType versions prior to 2.5.4 and represents a critical security issue that demonstrates the dangers of inadequate input validation in font processing systems. The vulnerability occurs when FreeType processes TrueType font files that contain embedded PNG images, creating a scenario where maliciously crafted font files can trigger system instability. The root cause stems from insufficient bounds checking on the rows and pitch parameters of PNG data during the loading process, allowing attackers to manipulate these values in ways that bypass normal validation mechanisms.
The technical exploitation of this vulnerability involves constructing a specially crafted .ttf font file containing a malicious PNG image with manipulated row and pitch values. When FreeType attempts to load this font file, the Load_SBit_Png function processes these invalid parameters without proper overflow protection, leading to integer overflow conditions that subsequently trigger heap-based buffer overflows. This class of vulnerability maps directly to CWE-190, which describes integer overflow conditions, and CWE-121, which covers stack-based buffer overflow conditions. The exploitation can result in denial of service scenarios where applications crash due to memory corruption, or potentially more severe outcomes including arbitrary code execution depending on the specific system configuration and memory layout.
The operational impact of CVE-2014-9665 extends across numerous applications and systems that rely on FreeType for font rendering, including web browsers, desktop applications, and server software. Attackers can leverage this vulnerability through various attack vectors such as malicious websites, email attachments, or document files that contain embedded fonts. The vulnerability's remote exploitation capability makes it particularly dangerous in web environments where users may unknowingly encounter malicious font files. According to ATT&CK framework, this vulnerability corresponds to T1203, which covers Exploitation for Client Execution, and T1068, which covers Exploitation for Privilege Escalation. The attack surface is broad as any application that processes font files, particularly those that support embedded image formats, becomes a potential target for exploitation.
Mitigation strategies for this vulnerability primarily involve upgrading to FreeType version 2.5.4 or later, which includes patches that properly validate the rows and pitch parameters during PNG data processing. System administrators should also implement defensive measures such as restricting font file processing in web applications and implementing strict input validation for all font-related data. Network-based defenses can include filtering font files at network boundaries and employing sandboxing techniques for font processing. Organizations should conduct comprehensive vulnerability assessments to identify all systems that may be exposed to this vulnerability, particularly those that process untrusted font files from external sources. The fix implemented in FreeType 2.5.4 demonstrates proper bounds checking and integer overflow protection mechanisms that prevent the manipulation of row and pitch values from causing memory corruption. Regular security updates and patch management processes are essential to maintain protection against similar vulnerabilities in font rendering libraries.