CVE-2012-1136 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 (invalid heap write operation and memory corruption) or possibly execute arbitrary code via crafted glyph or bitmap data in a BDF font that lacks an ENCODING field.
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Analysis
by VulDB Data Team • 04/13/2021
The vulnerability identified as CVE-2012-1136 represents a critical heap-based buffer overflow in the FreeType font rendering library that affects multiple applications including Mozilla Firefox Mobile. This flaw stems from inadequate input validation when processing BDF (Bitmap Distribution Format) font files that lack proper ENCODING fields. The vulnerability resides in the font parsing logic where the software fails to properly validate the structure and content of font data before attempting to write to memory locations. The issue manifests when FreeType encounters malformed BDF font data that does not contain the required ENCODING field, leading to unpredictable memory corruption patterns.
The technical exploitation of this vulnerability occurs through the manipulation of font rendering processes where crafted glyph or bitmap data triggers an invalid heap write operation. When the FreeType library attempts to parse BDF font files without proper ENCODING fields, it calculates memory offsets based on malformed data structures, resulting in memory corruption that can be leveraged for arbitrary code execution or denial of service. This vulnerability specifically affects applications that rely on FreeType for font rendering, particularly mobile browsers and desktop applications that process external font resources. The flaw demonstrates characteristics consistent with CWE-121 heap-based buffer overflow conditions where insufficient bounds checking leads to memory corruption.
The operational impact of CVE-2012-1136 extends beyond simple denial of service scenarios to potentially enable remote code execution attacks. Attackers can craft malicious BDF font files that, when processed by vulnerable applications, cause the target system to execute arbitrary code with the privileges of the affected application. This makes the vulnerability particularly dangerous in mobile environments where Firefox Mobile was impacted, as it could be exploited through web content or malicious attachments. The vulnerability affects not only the specific versions mentioned but any software that incorporates FreeType versions prior to 2.4.9, creating widespread exposure across numerous applications that depend on this font rendering library for proper text display functionality.
Mitigation strategies for CVE-2012-1136 primarily involve immediate patching of affected FreeType versions to 2.4.9 or later, which includes enhanced input validation and proper bounds checking for font data processing. System administrators should prioritize updating all affected applications, particularly mobile browsers and desktop software that utilize FreeType for font rendering. Additionally, implementing application whitelisting and font validation policies can provide defense-in-depth measures, while network-based intrusion detection systems can be configured to monitor for suspicious font file patterns. The vulnerability aligns with ATT&CK technique T1059.007 for process injection and T1499.004 for network denial of service, making it a significant concern for both enterprise security and mobile device protection. Organizations should also consider implementing sandboxing mechanisms for font processing and regular security assessments to identify other potential vulnerabilities in font rendering libraries.