CVE-2012-1139 in iOS
Summary
by MITRE
Array index error in 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 stack read operation and memory corruption) or possibly execute arbitrary code via crafted glyph data in a BDF font.
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Analysis
by VulDB Data Team • 05/01/2018
The vulnerability identified as CVE-2012-1139 represents a critical array index error within the FreeType font rendering library version 2.4.8 and earlier. This flaw exists in the handling of BDF (Bitmap Distribution Format) font files, which are commonly used for displaying text in various applications including web browsers and operating systems. The vulnerability specifically affects Mozilla Firefox Mobile versions prior to 10.0.4, though it potentially impacts numerous other software products that rely on FreeType for font processing. The issue stems from inadequate bounds checking when processing glyph data within BDF font files, creating a scenario where maliciously crafted font data can trigger unexpected behavior in the underlying memory management systems.
The technical nature of this vulnerability falls under CWE-129, which describes improper validation of array indices, and represents a classic buffer over-read condition that can lead to both denial of service and potential code execution. When FreeType processes a malformed BDF font file containing crafted glyph data, the library fails to properly validate the array indices used for accessing glyph information, leading to invalid memory reads. This invalid stack read operation occurs because the font parser attempts to access memory locations beyond the allocated buffer boundaries, which can result in memory corruption and system instability. The vulnerability's exploitation potential is significant as it can be triggered through web content, making it particularly dangerous for mobile browsers that process untrusted font data from remote servers.
The operational impact of CVE-2012-1139 extends beyond simple denial of service scenarios to potentially enable remote code execution, making it a severe security concern for affected systems. When exploited, this vulnerability can cause applications to crash or behave unpredictably, leading to service disruption for users. However, the more dangerous aspect involves the possibility of arbitrary code execution, which would allow attackers to gain control over the affected system. The vulnerability's exploitation requires an attacker to craft a malicious BDF font file and convince a user to view content that loads this font, typically through web pages or email attachments. This attack vector aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as the vulnerability could be leveraged to execute malicious code within the context of the affected application. The impact is particularly severe on mobile platforms where users frequently encounter web content from untrusted sources.
Mitigation strategies for CVE-2012-1139 primarily focus on updating affected software to versions that contain proper bounds checking and memory validation. Organizations should immediately upgrade FreeType to version 2.4.9 or later, which includes fixes for the array index error. For Mozilla Firefox Mobile, updating to version 10.0.4 or higher resolves the vulnerability. Additionally, implementing defensive programming practices such as enabling stack canaries, address space layout randomization, and other exploit mitigations can help reduce the effectiveness of potential exploitation attempts. Network administrators should also consider implementing content filtering measures that prevent the download and execution of suspicious font files. The vulnerability serves as a reminder of the importance of regular security updates and proper input validation in font rendering libraries, as these components are often overlooked in security assessments but can provide critical attack vectors for sophisticated adversaries.