CVE-2006-1988 in Safari
Summary
by MITRE
The WebTextRenderer(WebInternal) _CG_drawRun:style:geometry: function in Apple Safari 2.0.3 allows remote attackers to cause a denial of service (application crash) via an HTML LI tag with a large VALUE attribute (list item number), which triggers a null dereference in QPainter::drawText, probably due to a failed memory allocation that uses the VALUE.
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Analysis
by VulDB Data Team • 06/17/2019
The vulnerability described in CVE-2006-1988 represents a critical denial of service flaw within Apple Safari version 2.0.3 that stems from improper handling of HTML list item attributes. This issue specifically targets the WebTextRenderer component within Safari's WebInternal framework, where the _CG_drawRun:style:geometry: function fails to adequately validate input parameters when processing HTML LI tags. The flaw manifests when a remote attacker crafts malicious HTML content containing an LI element with an excessively large VALUE attribute, which serves as the list item number identifier. This particular vulnerability falls under the category of improper input validation and memory management issues that are commonly classified as CWE-129 and CWE-476 within the Common Weakness Enumeration framework.
The technical execution of this vulnerability occurs through a specific code path that involves the QPainter::drawText function, which is part of Qt's graphics rendering system that Safari utilizes for text display operations. When the browser encounters an LI tag with an oversized VALUE attribute, the rendering engine attempts to process this value through the problematic function chain, ultimately leading to a null pointer dereference condition. The underlying cause appears to be a failed memory allocation attempt that occurs during the text rendering process, where the system allocates memory for the large numerical value but fails to properly handle the subsequent text drawing operation. This failure results in a segmentation fault or application crash, effectively rendering the browser unusable until restart.
The operational impact of this vulnerability extends beyond simple service disruption, as it represents a potential vector for more sophisticated attacks within the context of the broader ATT&CK framework. While the immediate effect is a denial of service condition that forces users to restart their browser, this vulnerability demonstrates the broader class of issues that can compromise application stability in web browsers. The flaw affects the core rendering engine of Safari, which means that any web page containing maliciously crafted HTML could trigger this condition, making it particularly dangerous in environments where users may encounter untrusted content. The vulnerability also highlights the importance of proper memory management and input validation in graphics rendering components, as similar issues could potentially be exploited to execute arbitrary code or escalate privileges, though the current manifestation is limited to denial of service.
Mitigation strategies for this vulnerability should focus on both immediate patching and defensive programming practices. The most effective solution involves updating to a patched version of Safari that addresses the input validation issue in the WebTextRenderer component, which would typically include bounds checking for attribute values and proper error handling for memory allocation failures. Additionally, browser vendors should implement robust input sanitization mechanisms that validate numeric attributes against reasonable upper limits, preventing the processing of excessively large values that could trigger memory allocation failures. From a defensive standpoint, users should be encouraged to maintain updated browser versions and avoid visiting untrusted websites, while system administrators should consider implementing web content filtering solutions that can detect and block malicious HTML patterns. The vulnerability also underscores the need for comprehensive testing of graphics rendering components, particularly those that interface with external input sources, as these areas often represent attack surfaces that are difficult to detect through standard security assessments.