CVE-2006-1986 in Safari
Summary
by MITRE
Apple Safari 2.0.3 allows remote attackers to cause a denial of service and possibly execute code via a large CELLSPACING attribute in a TABLE tag, which triggers an error in KWQListIteratorImpl::KWQListIteratorImpl.
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Analysis
by VulDB Data Team • 06/17/2019
This vulnerability affects Apple Safari version 2.0.3 and represents a classic buffer overflow condition that can be exploited through malformed HTML content. The flaw manifests when the browser encounters a TABLE tag with an excessively large CELLSPACING attribute value, which triggers an error within the KWQListIteratorImpl class of the browser's rendering engine. The vulnerability stems from inadequate input validation and memory management within the web rendering component, specifically in how the browser processes table cell spacing parameters. This type of vulnerability falls under the category of improper input validation as defined by CWE-20, where the application fails to properly validate or sanitize user-supplied data before processing it. The error condition occurs during the initialization of a list iterator object, suggesting that the browser's HTML parser does not adequately handle extreme values for table layout attributes.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable remote code execution, making it particularly dangerous in malicious web page scenarios. When a user visits a specially crafted webpage containing the malformed TABLE tag, the browser's rendering engine attempts to process the excessive CELLSPACING value and fails during the KWQListIteratorImpl constructor phase. This failure can result in memory corruption that may allow attackers to inject and execute arbitrary code on the victim's system. The vulnerability aligns with ATT&CK technique T1203, which involves exploiting software vulnerabilities to gain remote code execution capabilities. The attack vector requires the user to navigate to a malicious webpage, making it a client-side exploitation method that relies on social engineering to succeed.
The technical flaw demonstrates a lack of proper bounds checking and memory allocation validation within the browser's HTML parsing and rendering subsystem. The KWQListIteratorImpl class appears to assume valid input parameters and does not implement adequate safeguards against excessively large numerical values that could cause stack or heap corruption. This vulnerability represents a failure in the principle of least privilege and input sanitization, where the browser should reject or normalize malformed input rather than attempting to process it directly. The memory corruption resulting from this flaw could be exploited through various techniques including stack smashing or heap spraying, depending on the specific memory layout and browser implementation details. Organizations should note that this vulnerability was present in older browser versions and highlights the importance of keeping web browsers updated to address known security flaws.
Mitigation strategies should focus on immediate browser updates to newer versions that contain patches for this vulnerability, as well as implementing network-based protections such as web application firewalls that can detect and block malicious HTML content. Users should be educated about the risks of visiting untrusted websites and the importance of keeping their browser software up to date. Network administrators should consider implementing content filtering solutions that can identify and block suspicious HTML constructs before they reach end users. The vulnerability also underscores the importance of secure coding practices and thorough testing of input validation mechanisms, particularly in web rendering engines where malformed input can lead to severe security consequences. Regular security assessments and penetration testing should be conducted to identify similar vulnerabilities in web applications and browser implementations.