CVE-2008-1808 in FreeType
Summary
by MITRE
Multiple off-by-one errors in FreeType2 before 2.3.6 allow context-dependent attackers to execute arbitrary code via (1) a crafted table in a Printer Font Binary (PFB) file or (2) a crafted SHC instruction in a TrueType Font (TTF) file, which triggers a heap-based buffer overflow.
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Analysis
by VulDB Data Team • 08/12/2019
The vulnerability identified as CVE-2008-1808 represents a critical security flaw within the FreeType2 font rendering library, which is widely deployed across operating systems and applications for handling font processing. This vulnerability affects FreeType2 versions prior to 2.3.6 and stems from multiple off-by-one errors that create conditions for heap-based buffer overflows. The flaw specifically manifests when the library processes malformed font files, particularly PFB (Printer Font Binary) and TTF (TrueType Font) formats, making it a significant concern for systems that rely on proper font handling mechanisms. The vulnerability's context-dependent nature means that exploitation requires specific conditions and crafted malicious input, but the potential impact is severe enough to warrant immediate attention from security professionals and system administrators.
The technical implementation of this vulnerability involves two distinct attack vectors that exploit different aspects of the FreeType2 library's font parsing mechanisms. The first vector targets PFB files through crafted table structures that cause an off-by-one error during memory allocation, leading to heap corruption when the library attempts to read beyond allocated buffer boundaries. The second vector operates on TTF files by manipulating SHC (Scalable Header Compression) instructions in a manner that triggers similar buffer overflow conditions. Both attack scenarios leverage the fundamental flaw in how FreeType2 handles memory boundaries when processing font metadata, specifically in the way it calculates and allocates memory for font table structures. These off-by-one errors are classified under CWE-129, which describes improper validation of length values, and fall within the broader category of buffer overflow vulnerabilities that can lead to arbitrary code execution. The heap-based nature of these overflows means that attackers can potentially manipulate memory layout to achieve code execution, making these vulnerabilities particularly dangerous in environments where font processing occurs without proper input sanitization.
The operational impact of CVE-2008-1808 extends far beyond simple font rendering issues, as FreeType2 is integrated into numerous software applications and operating system components that handle font processing. Systems that process untrusted font files, such as web browsers, document viewers, email clients, and graphic design applications, become vulnerable to remote code execution attacks when exposed to maliciously crafted font files. The context-dependent nature of the vulnerability means that exploitation typically requires social engineering or specific attack scenarios where users encounter crafted font files, but the potential for automated exploitation exists in certain configurations. This vulnerability directly maps to ATT&CK technique T1068, which describes the use of legitimate credentials and system privileges to execute malicious code, as the buffer overflow conditions can be leveraged to gain control over the affected system's execution flow. The widespread adoption of FreeType2 across Linux distributions, Windows systems, and various applications means that a successful exploitation could potentially affect hundreds of thousands of systems, making this vulnerability particularly concerning from a threat intelligence perspective.
Mitigation strategies for CVE-2008-1808 should prioritize immediate patching of affected FreeType2 installations to version 2.3.6 or later, which contains the necessary fixes for the identified off-by-one errors. System administrators should implement additional defensive measures including input validation for font files, sandboxing font processing components, and monitoring for unusual font processing activities that might indicate exploitation attempts. The vulnerability highlights the importance of proper memory management practices and input validation in font rendering libraries, which should be addressed through comprehensive code reviews and security testing. Organizations should also consider implementing application whitelisting policies that restrict font processing to trusted sources and establish automated scanning mechanisms for font files in email attachments, web downloads, and other potentially untrusted content sources. The remediation process should include thorough testing of patched systems to ensure that the vulnerability has been properly addressed without introducing regressions in font rendering functionality, as the patched versions may alter how certain font files are processed, potentially affecting legitimate applications that depend on specific font handling behaviors.