CVE-2010-3814 in FreeType
Summary
by MITRE
Heap-based buffer overflow in the Ins_SHZ function in ttinterp.c in FreeType 2.4.3 and earlier allows remote attackers to execute arbitrary code or cause a denial of service (application crash) via a crafted SHZ bytecode instruction, related to TrueType opcodes, as demonstrated by a PDF document with a crafted embedded font.
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Analysis
by VulDB Data Team • 10/05/2021
The vulnerability identified as CVE-2010-3814 represents a critical heap-based buffer overflow affecting the FreeType font rendering library version 2.4.3 and earlier. This flaw resides within the Ins_SHZ function located in the ttinterp.c file, which processes TrueType bytecode instructions during font interpretation. The vulnerability manifests when processing crafted SHZ (SHift Zone) bytecode instructions that are embedded within font files, particularly those embedded in PDF documents. The issue stems from insufficient bounds checking during the interpretation of these specific TrueType opcodes, creating a condition where malicious input can overwrite adjacent memory regions in the heap allocation.
The technical exploitation of this vulnerability occurs through the manipulation of TrueType font instructions that control how font glyphs are rendered on screen or in print. When a PDF document containing a maliciously crafted embedded font is processed by an application using FreeType 2.4.3 or earlier, the Ins_SHZ function fails to properly validate the size and boundaries of the data being read from the bytecode stream. This allows attackers to inject malformed data that exceeds the allocated buffer space, leading to memory corruption that can be leveraged for arbitrary code execution or system crashes. The vulnerability falls under CWE-121 Heap-based Buffer Overflow, which is classified as a critical weakness in memory safety that directly enables code execution attacks.
The operational impact of CVE-2010-3814 extends beyond simple denial of service scenarios to encompass full system compromise capabilities. Applications that rely on FreeType for font rendering, including web browsers, PDF viewers, and document processing software, become vulnerable to remote code execution attacks when processing maliciously crafted documents. This vulnerability is particularly dangerous because it can be exploited through common document formats like PDF, which are widely distributed and frequently opened by end users. The attack surface is broad since many applications use FreeType as their primary font rendering engine, making this vulnerability a significant threat vector in enterprise and consumer environments alike. The ATT&CK framework categorizes this as a code injection technique under the T1059.007 sub-technique, where attackers leverage library vulnerabilities to execute malicious code.
Mitigation strategies for CVE-2010-3814 require immediate patching of affected FreeType library versions to 2.4.4 or later, which contain the necessary fixes for the heap buffer overflow. System administrators should prioritize updating all applications that depend on FreeType, particularly those handling untrusted document content such as web browsers, PDF readers, and document management systems. Additional protective measures include implementing sandboxing mechanisms for document processing, enabling strict memory protection features like DEP and ASLR, and deploying intrusion detection systems that can identify suspicious font processing patterns. Organizations should also consider restricting the use of embedded fonts in sensitive environments and implementing content filtering for PDF documents to prevent execution of potentially malicious bytecode instructions. The vulnerability demonstrates the critical importance of maintaining up-to-date font rendering libraries and highlights the need for comprehensive security testing of font processing components in applications that handle untrusted content.