CVE-2012-1135 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 read operation and memory corruption) or possibly execute arbitrary code via vectors involving the NPUSHB and NPUSHW instructions in a TrueType font.
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Analysis
by VulDB Data Team • 04/13/2021
The vulnerability identified as CVE-2012-1135 represents a critical security flaw in the FreeType font rendering library that affects multiple applications including Mozilla Firefox Mobile. This issue stems from improper handling of specific TrueType font instructions, namely NPUSHB and NPUSHW, which are used to push data onto the interpreter stack during font processing. The vulnerability exists in FreeType versions prior to 2.4.9 and specifically impacts mobile browsers and applications that rely on this font rendering engine. The flaw manifests when processing maliciously crafted TrueType fonts that contain malformed NPUSHB and NPUSHW instructions, leading to unpredictable behavior in the font interpreter.
The technical implementation of this vulnerability involves a heap-based buffer overflow condition that occurs during the interpretation of font data. When the FreeType library encounters these specific instructions in malformed fonts, it fails to properly validate the data being pushed onto the interpreter stack, resulting in an invalid heap read operation. This memory corruption can potentially be exploited by attackers to execute arbitrary code on affected systems. The vulnerability operates at the intersection of font processing and memory management, making it particularly dangerous as it can be triggered simply by viewing a malicious font file, without requiring user interaction beyond normal font rendering operations. This type of vulnerability is classified as a memory safety issue and aligns with CWE-125, which covers out-of-bounds reads, and CWE-787, which addresses out-of-bounds writes.
The operational impact of CVE-2012-1135 is significant, particularly in mobile environments where Firefox Mobile was vulnerable. Attackers could craft malicious TrueType font files that, when rendered by the affected software, would trigger the memory corruption and potentially allow remote code execution. This capability makes the vulnerability particularly dangerous for mobile users who may encounter such fonts in web content, email attachments, or other digital media. The vulnerability's exploitation potential extends beyond simple denial of service, as the memory corruption could be leveraged to bypass security mechanisms or execute malicious payloads. The impact is further amplified by the widespread use of FreeType in various applications and operating systems, creating a broad attack surface. According to ATT&CK framework, this vulnerability maps to T1059.007 for command and scripting interpreter and T1203 for exploitation for execution, as it allows for arbitrary code execution through font processing.
Mitigation strategies for this vulnerability primarily involve updating to FreeType version 2.4.9 or later, which includes proper bounds checking and validation for the NPUSHB and NPUSHW instructions. System administrators should prioritize patching affected applications, particularly mobile browsers and any software that utilizes the vulnerable FreeType library. Additionally, implementing content filtering measures to block or sandbox font files from untrusted sources can provide an additional layer of protection. The vulnerability highlights the importance of proper input validation in font rendering libraries and demonstrates how seemingly benign font processing operations can become security risks. Organizations should also consider implementing security monitoring to detect potential exploitation attempts involving font-based attacks, as these vulnerabilities often go undetected until they are actively exploited in the wild. The remediation approach should include comprehensive testing of patched versions to ensure that the fix does not introduce regressions in font rendering functionality while maintaining the security improvements.