CVE-2014-9671 in FreeType
Summary
by MITRE
Off-by-one error in the pcf_get_properties function in pcf/pcfread.c in FreeType before 2.5.4 allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) via a crafted PCF file with a 0xffffffff size value that is improperly incremented.
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Analysis
by VulDB Data Team • 03/08/2022
The vulnerability identified as CVE-2014-9671 represents a critical off-by-one error within the FreeType font rendering library that affects versions prior to 2.5.4. This flaw exists within the pcf_get_properties function located in the pcf/pcfread.c source file, demonstrating a classic buffer overflow condition that can be exploited remotely to execute denial of service attacks. The vulnerability specifically targets the PCF (Portable Compiled Format) font file processing component of FreeType, which is widely used across operating systems and applications for font rendering operations.
The technical implementation of this vulnerability stems from improper handling of size values during PCF file parsing operations. When a maliciously crafted PCF file contains a 0xffffffff size value, the pcf_get_properties function fails to properly validate or increment this value before processing it. This incorrect increment operation results in an integer overflow condition that ultimately leads to a NULL pointer dereference when the application attempts to access memory locations that have not been properly allocated or initialized. The flaw operates through a fundamental miscalculation in arithmetic operations where the size parameter exceeds the maximum representable value for the data type, causing the system to behave unpredictably and crash.
The operational impact of this vulnerability extends across numerous systems and applications that rely on FreeType for font processing, including web browsers, desktop environments, mobile operating systems, and server applications. Attackers can exploit this vulnerability by crafting specially formatted PCF font files that trigger the malformed size value condition, leading to complete application crashes and potential system instability. This denial of service condition can be particularly damaging in server environments where continuous availability is critical, as it allows attackers to disrupt legitimate service operations without requiring elevated privileges or complex exploitation techniques. The vulnerability affects both client-side and server-side implementations, making it a widespread concern across multiple computing platforms and environments.
Mitigation strategies for CVE-2014-9671 primarily focus on immediate software updates and patches to FreeType versions 2.5.4 and later, which contain the necessary fixes to properly handle size value validation and prevent the integer overflow condition. System administrators should prioritize patching all affected systems, particularly those running web browsers, desktop environments, or server applications that process external font files. Additional protective measures include implementing strict file validation mechanisms for font processing, deploying sandboxing techniques to isolate font rendering operations, and monitoring for suspicious file upload activities that could indicate attempts to exploit this vulnerability. Organizations should also consider implementing network-level controls to restrict access to potentially malicious font files and establish robust incident response procedures to address potential exploitation attempts. This vulnerability aligns with CWE-129, which describes improper validation of array indices and buffer bounds, and can be mapped to ATT&CK technique T1203, which involves exploitation of software vulnerabilities for denial of service attacks. The flaw demonstrates the importance of proper input validation and integer arithmetic handling in security-critical applications, particularly those involved in processing untrusted binary data formats.