CVE-2014-9673 in FreeType
Summary
by MITRE
Integer signedness error in the Mac_Read_POST_Resource function in base/ftobjs.c in FreeType before 2.5.4 allows remote attackers to cause a denial of service (heap-based buffer overflow) or possibly have unspecified other impact via a crafted Mac font.
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Analysis
by VulDB Data Team • 03/09/2022
The vulnerability identified as CVE-2014-9673 represents a critical integer signedness error within the FreeType font rendering library, specifically affecting the Mac_Read_POST_Resource function in the base/ftobjs.c source file. This flaw exists in FreeType versions prior to 2.5.4 and demonstrates a classic software security weakness that can be exploited remotely to cause significant system instability. The vulnerability arises from improper handling of integer values during font resource processing, creating conditions where signed integer variables are incorrectly used in contexts that expect unsigned values, leading to unpredictable behavior in memory allocation and buffer management operations.
The technical implementation of this vulnerability stems from a fundamental flaw in how the font library processes Mac-specific font resources, particularly those stored in the POST resource format. When the Mac_Read_POST_Resource function encounters a crafted malicious font file, the signedness error causes integer overflow conditions that result in heap-based buffer overflows. This occurs because the library fails to properly validate or convert integer values that represent resource sizes or offsets, allowing attackers to manipulate these values into causing memory corruption. The flaw operates at the intersection of memory management and integer arithmetic, where signed integer variables are used in contexts where unsigned values are expected, creating opportunities for attackers to control memory allocation decisions.
From an operational perspective, this vulnerability presents a substantial risk to systems that process untrusted font data, particularly those running applications that utilize FreeType for font rendering such as web browsers, document viewers, and graphic applications. The remote exploitation capability means that attackers can trigger the vulnerability through malicious font files delivered via web content, email attachments, or file sharing systems. The potential impacts range from denial of service conditions where applications crash or become unresponsive, to more severe consequences including arbitrary code execution in vulnerable systems. The unspecified other impacts mentioned in the CVE description suggest that under certain conditions, this vulnerability could potentially allow for privilege escalation or information disclosure, making it particularly dangerous in enterprise environments where font processing is common.
The vulnerability aligns with CWE-190, which describes integer overflow conditions, and demonstrates characteristics consistent with ATT&CK technique T1203, where adversaries leverage software vulnerabilities to gain access to systems through application exploitation. Organizations using FreeType libraries should prioritize immediate patching to version 2.5.4 or later, as this update contains the necessary fixes for the integer signedness error. Additional mitigations include implementing strict font validation procedures, deploying web application firewalls to filter suspicious font content, and configuring applications to sanitize font data before processing. Network segmentation and monitoring for unusual font processing activities can also help detect potential exploitation attempts. The vulnerability underscores the importance of thorough input validation and proper integer handling in font processing libraries, as these components often serve as attack vectors due to their widespread use and the complex nature of font formats that require extensive parsing and memory management operations.