CVE-2015-9381 in FreeType
Summary
by MITRE
FreeType before 2.6.1 has a heap-based buffer over-read in T1_Get_Private_Dict in type1/t1parse.c.
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Analysis
by VulDB Data Team • 12/11/2023
The vulnerability identified as CVE-2015-9381 represents a critical heap-based buffer over-read flaw within the FreeType font rendering library, specifically affecting versions prior to 2.6.1. This issue resides in the T1_Get_Private_Dict function located in the type1/t1parse.c source file, which handles parsing of Type 1 font files. The flaw manifests when processing malformed or maliciously crafted Type 1 font files that contain improperly structured private dictionary data, leading to memory access violations that can potentially be exploited for arbitrary code execution or denial of service attacks.
The technical implementation of this vulnerability stems from inadequate bounds checking during the parsing of Type 1 font private dictionaries. When FreeType encounters a Type 1 font file with malformed data structures, the T1_Get_Private_Dict function fails to properly validate the size and boundaries of memory allocations before reading data from the heap. This oversight allows an attacker to craft a font file that causes the parser to read beyond allocated memory boundaries, potentially accessing sensitive data or causing application crashes. The vulnerability operates at the intersection of software security and font processing, demonstrating how legacy font parsing code can contain fundamental memory safety issues that persist across multiple versions.
From an operational impact perspective, this vulnerability affects any application or system that utilizes FreeType for font rendering, including web browsers, desktop applications, document viewers, and server-side applications processing font files. The over-read condition can lead to unpredictable behavior ranging from application crashes to potential information disclosure, where adjacent memory contents might be exposed to attackers. Given FreeType's widespread adoption across operating systems and software platforms, the potential attack surface is extensive, making this vulnerability particularly concerning for security professionals managing large-scale deployments. The vulnerability aligns with CWE-125, which identifies "Out-of-bounds Read" as a common weakness in software systems, and can be categorized under ATT&CK technique T1203 for "Exploitation for Client Execution" when leveraged in web-based attacks.
Mitigation strategies for CVE-2015-9381 primarily focus on immediate software updates to FreeType version 2.6.1 or later, which includes patches addressing the buffer over-read condition through proper input validation and memory boundary checks. Organizations should implement comprehensive patch management procedures to ensure all systems utilizing FreeType are updated promptly. Additional defensive measures include implementing strict font file validation mechanisms, deploying sandboxing techniques for font processing, and monitoring for suspicious font file patterns that might indicate exploitation attempts. Network-based detection systems can be enhanced to identify malformed Type 1 font files in traffic, while application-level protections such as address space layout randomization and stack canaries can provide additional layers of defense against potential exploitation attempts. The vulnerability serves as a reminder of the importance of maintaining up-to-date font rendering libraries and implementing robust input validation practices in security-critical applications.