CVE-2017-7864 in FreeType 2
Summary
by MITRE
FreeType 2 before 2017-02-02 has an out-of-bounds write caused by a heap-based buffer overflow related to the tt_size_reset function in truetype/ttobjs.c.
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Analysis
by VulDB Data Team • 11/29/2022
The vulnerability identified as CVE-2017-7864 represents a critical heap-based buffer overflow in the FreeType 2 font rendering library, specifically affecting versions prior to the February 2, 2017 release. This flaw exists within the truetype/ttobjs.c source file at the tt_size_reset function, where improper bounds checking allows maliciously crafted font files to trigger unauthorized memory writes beyond allocated buffer boundaries. The issue stems from inadequate input validation when processing TrueType font data structures, particularly during size reset operations that occur when font metrics are recalculated or modified. Such buffer overflows create significant security risks as they can be exploited to execute arbitrary code, corrupt memory structures, or cause application crashes that may lead to denial of service conditions. The vulnerability is particularly concerning because FreeType is widely used across operating systems, web browsers, and applications for font rendering, making it a prime target for attackers seeking to exploit font processing routines. The out-of-bounds write condition occurs when the tt_size_reset function fails to properly validate the dimensions of font metrics arrays before writing data to heap-allocated memory regions, allowing attackers to overwrite adjacent memory locations with controlled data. This type of vulnerability aligns with CWE-121, heap-based buffer overflow, and can be categorized under ATT&CK technique T1059.007 for process injection through font rendering components. The impact extends beyond simple crashes to potential privilege escalation scenarios, especially when FreeType is used in sandboxed environments or applications with elevated privileges. Attackers can craft specially formatted TrueType font files that, when processed by vulnerable applications, trigger the buffer overflow condition and potentially execute malicious payloads. The vulnerability demonstrates the critical importance of proper memory management and input validation in font processing libraries, as these components are frequently invoked during normal application operation and may be exposed to untrusted font data from various sources. Organizations using affected FreeType versions should prioritize immediate patching to prevent exploitation, as the vulnerability can be leveraged in supply chain attacks, web-based exploits, or through malicious document attachments that trigger font rendering. The flaw also highlights the need for comprehensive fuzzing and security testing of font rendering engines, as these libraries often receive minimal security scrutiny despite their widespread use and critical role in system functionality. Remediation efforts should include not only updating to FreeType 2.7 or later but also implementing additional security controls such as application sandboxing, input validation, and monitoring for unusual font processing activities that may indicate exploitation attempts.