CVE-2012-1143 in iOS
Summary
by MITRE
FreeType before 2.4.9, as used in Mozilla Firefox Mobile before 10.0.4 and other products, allows remote attackers to cause a denial of service (divide-by-zero error) via a crafted font.
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Analysis
by VulDB Data Team • 04/13/2021
The vulnerability identified as CVE-2012-1143 represents a critical divide-by-zero error within the FreeType font rendering library that affects multiple software products including Mozilla Firefox Mobile versions prior to 10.0.4. This flaw exists in FreeType versions before 2.4.9 and demonstrates how font processing components can become attack vectors for denial of service attacks. The vulnerability is particularly concerning because it allows remote attackers to exploit a mathematical error that occurs during font rendering operations, potentially leading to application crashes and system instability. The issue stems from improper input validation within the font parsing routines where division operations are performed without adequate checks for zero denominators, creating a condition that can be triggered by maliciously crafted font files.
The technical implementation of this vulnerability involves the FreeType library's handling of font metrics and glyph rendering processes where specific font parameters can lead to division by zero during mathematical computations. When a malicious font file is processed by the vulnerable FreeType component, the library attempts to perform arithmetic operations with zero as a denominator, causing the application to terminate abruptly. This type of error falls under CWE-369, which specifically addresses the divide by zero weakness, and represents a classic example of improper input validation in system components. The flaw demonstrates how font rendering engines can become attack surfaces when they fail to properly sanitize input data, particularly when dealing with external font files that may contain malformed or malicious parameters.
The operational impact of CVE-2012-1143 extends beyond simple application crashes to potentially affect user experience and system availability across affected platforms. Mobile browsers like Firefox Mobile that rely on FreeType for font rendering become vulnerable to remote exploitation, allowing attackers to disrupt service for users accessing web content that includes malicious fonts. The vulnerability can be exploited through various attack vectors including web pages, email attachments, or any content that triggers font rendering, making it particularly dangerous in mobile environments where users may encounter such content unexpectedly. This type of attack aligns with ATT&CK technique T1059.007 for command and scripting interpreter, specifically targeting the execution environment through font processing components. The potential for widespread impact exists because many applications and operating systems depend on FreeType for font handling, creating a cascading effect across multiple platforms.
Mitigation strategies for CVE-2012-1143 primarily focus on updating to patched versions of FreeType library where the divide-by-zero condition has been addressed through proper input validation and error handling. Organizations should prioritize updating Firefox Mobile to version 10.0.4 or later, and ensure all other affected products have received appropriate patches. System administrators should implement network monitoring to detect potential exploitation attempts through suspicious font content, while security teams should consider implementing application whitelisting policies to restrict font file processing in critical environments. The fix typically involves adding proper boundary checks before division operations and implementing graceful error handling that prevents application termination. Additionally, implementing sandboxing techniques for font processing operations can limit the potential impact of similar vulnerabilities in the future, aligning with defense-in-depth strategies recommended by security frameworks and standards.