CVE-2011-3193 in Digia
Summary
by MITRE
Heap-based buffer overflow in the Lookup_MarkMarkPos function in the HarfBuzz module (harfbuzz-gpos.c), as used by Qt before 4.7.4 and Pango, allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via a crafted font file.
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Analysis
by VulDB Data Team • 12/03/2021
The vulnerability identified as CVE-2011-3193 represents a critical heap-based buffer overflow within the HarfBuzz text shaping engine, specifically affecting the Lookup_MarkMarkPos function in the harfbuzz-gpos.c module. This flaw exists in the core text processing components that are widely integrated into major software ecosystems including Qt versions prior to 4.7.4 and Pango text rendering libraries. The vulnerability stems from insufficient bounds checking when processing font files that contain specially crafted mark positioning data, creating a condition where malicious input can overwrite adjacent memory regions in the heap allocation space. Such buffer overflow conditions are particularly dangerous because they can lead to unpredictable program behavior and potential code execution.
The technical exploitation of this vulnerability occurs when applications utilizing HarfBuzz for text rendering process font files containing malformed mark mark positioning entries. During the Lookup_MarkMarkPos function execution, the software fails to validate the size and structure of input data before attempting to copy or process it into allocated memory buffers. This allows attackers to craft font files with oversized or malformed mark positioning data that exceeds the allocated buffer boundaries, causing memory corruption that can result in application crashes or potentially arbitrary code execution. The vulnerability specifically targets the heap memory management system, making it particularly challenging to detect and prevent through standard input validation mechanisms.
The operational impact of CVE-2011-3193 extends beyond simple denial of service scenarios to encompass potential remote code execution capabilities that could be leveraged by attackers in various attack vectors. Applications that rely on HarfBuzz for text rendering including web browsers, office suites, desktop environments, and graphic design software become vulnerable when processing untrusted font content. The vulnerability's widespread presence in the Qt and Pango ecosystems means that a significant portion of modern software applications could be affected, particularly those that handle user-provided or third-party font files. This makes the vulnerability especially attractive to attackers seeking to exploit it in real-world scenarios, as it requires minimal user interaction beyond the simple act of opening or rendering content with affected fonts.
Organizations and developers must implement comprehensive mitigation strategies to address this vulnerability, starting with immediate patching of affected software versions. The primary recommendation involves upgrading to Qt 4.7.4 or later versions and ensuring Pango installations are updated to patched releases that contain fixed implementations of the Lookup_MarkMarkPos function. Additional defensive measures should include implementing strict input validation for font files, deploying sandboxing mechanisms for font processing, and utilizing memory protection techniques such as stack canaries and address space layout randomization. Security practitioners should also consider implementing network-based intrusion detection systems that can identify suspicious font file patterns and monitor for exploitation attempts. This vulnerability aligns with CWE-121 heap-based buffer overflow classifications and represents a significant concern within the ATT&CK framework under the privilege escalation and code execution tactics, particularly when considering the widespread adoption of affected libraries across multiple software platforms and operating systems.