CVE-2009-2655 in Internet Explorer
Summary
by MITRE
mshtml.dll in Microsoft Internet Explorer 7 and 8 on Windows XP SP3 allows remote attackers to cause a denial of service (application crash) by calling the JavaScript findText method with a crafted Unicode string in the first argument, and only one additional argument, as demonstrated by a second argument of -1.
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Analysis
by VulDB Data Team • 12/07/2024
The vulnerability described in CVE-2009-2655 represents a critical denial of service flaw within Microsoft Internet Explorer 7 and 8 running on Windows XP Service Pack 3 systems. This issue specifically targets the mshtml.dll component which serves as the core rendering engine for web content in Internet Explorer. The vulnerability manifests when the JavaScript findText method is invoked with a specially crafted Unicode string as its first parameter, combined with only a single additional argument. This particular combination triggers an application crash that results in a complete denial of service for the affected browser instance.
The technical implementation of this vulnerability stems from inadequate input validation within the findText JavaScript method implementation in the mshtml.dll library. When Internet Explorer processes the findText method call with the malformed Unicode string and the specific argument pattern of -1, the underlying memory management and string parsing routines fail to properly handle the edge case scenario. This failure leads to memory corruption or invalid memory access conditions that cause the application to terminate unexpectedly. The vulnerability is particularly concerning because it requires minimal user interaction to exploit, as the malicious JavaScript code can be embedded within web pages or delivered through various attack vectors such as phishing emails or compromised websites.
From an operational impact perspective, this vulnerability presents significant risks to organizations relying on Internet Explorer 7 and 8 for their web browsing activities. The denial of service condition affects not only individual user sessions but can also disrupt business operations when multiple users are simultaneously accessing web applications or services through vulnerable browsers. The attack vector is particularly dangerous because it can be executed remotely without requiring any special privileges or user interaction beyond visiting a malicious webpage. The vulnerability aligns with CWE-129, which addresses improper validation of length of input buffers, and demonstrates how inadequate bounds checking in string handling operations can lead to application instability. This flaw also maps to ATT&CK technique T1203, which involves legitimate user privileges to perform actions that can cause system instability through application-level exploits.
Organizations affected by this vulnerability should implement immediate mitigations including applying the relevant Microsoft security patches released in response to this CVE. The patch addresses the root cause by implementing proper input validation for the findText method parameters and strengthening the memory handling routines within mshtml.dll. Alternative mitigations include configuring Internet Explorer security settings to restrict JavaScript execution, implementing content filtering solutions, and deploying network-based intrusion detection systems that can identify and block malicious JavaScript patterns. For environments where patching is not immediately feasible, browser isolation techniques and user education about avoiding untrusted websites can provide temporary protection. The vulnerability underscores the importance of maintaining up-to-date security patches and demonstrates how seemingly minor implementation flaws in core browser components can result in significant operational disruptions and potential security risks.