CVE-2006-6955 in Web Browser
Summary
by MITRE
Opera allows remote attackers to cause a denial of service (application crash) via a web page that contains a large number of nested marquee tags, a related issue to CVE-2006-2723.
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Analysis
by VulDB Data Team • 10/07/2017
The vulnerability described in CVE-2006-6955 represents a classic denial of service flaw affecting the Opera web browser implementation. This issue specifically targets the browser's handling of nested marquee elements, which are html tags used to create scrolling text effects on web pages. The vulnerability arises when a malicious web page contains an excessive number of nested marquee tags, causing the browser to consume excessive system resources and ultimately crash. This type of vulnerability falls under the category of resource exhaustion attacks where the attacker leverages the browser's parsing logic to consume memory and processing power beyond normal operational limits.
The technical root cause of this vulnerability stems from inadequate input validation and resource management within Opera's html parser. When the browser encounters deeply nested marquee elements, it recursively processes each nested tag without proper bounds checking or resource limiting mechanisms. This recursive processing creates a stack overflow condition or excessive memory allocation that leads to application instability and eventual crash. The vulnerability is particularly concerning because it demonstrates how seemingly benign html elements can be weaponized to create denial of service conditions. This flaw aligns with CWE-400 which categorizes improper resource management as a fundamental weakness in software design, and specifically relates to CWE-121 which deals with stack-based buffer overflow conditions.
The operational impact of this vulnerability extends beyond simple application instability to potentially affect broader system security posture. When exploited, this denial of service condition can be used by attackers to disrupt legitimate browser usage, potentially affecting users in environments where browser stability is critical. The vulnerability's relationship to CVE-2006-2723 indicates a pattern of similar issues affecting web browser implementations, suggesting that the underlying parsing logic may have systematic weaknesses in handling nested html structures. From an adversarial perspective, this vulnerability could be exploited in conjunction with other attack vectors to create more sophisticated attacks, particularly in environments where users might be tricked into visiting malicious web pages through social engineering techniques.
Mitigation strategies for this vulnerability should focus on both immediate defensive measures and long-term architectural improvements. Browser vendors should implement proper bounds checking and resource limiting for html element processing, particularly for nested structures that could lead to excessive recursion. The implementation should include stack depth limits and memory allocation thresholds to prevent resource exhaustion conditions. Additionally, users should be advised to avoid visiting untrusted web sites and to keep their browser software updated with the latest security patches. This vulnerability demonstrates the importance of input validation and proper resource management in web browser security, aligning with ATT&CK technique T1499 which covers resource exhaustion attacks, and specifically targeting the browser rendering engine as a point of exploitation. Organizations should consider implementing web content filtering solutions to prevent access to known malicious sites and establish incident response procedures for handling browser-based denial of service incidents. The vulnerability also highlights the need for regular security testing of web browser components, particularly those handling user-provided content, to identify and remediate similar resource exhaustion conditions before they can be exploited by malicious actors.