CVE-2009-2668 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 6 through 6.0.2900.2180 and 7 through 7.0.6000.16473 allows remote attackers to cause a denial of service (CPU consumption) via an XML document composed of a long series of start-tags with no corresponding end-tags, a related issue to CVE-2009-1232.
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Analysis
by VulDB Data Team • 08/13/2021
Microsoft Internet Explorer versions 6 through 6.0.2900.2180 and 7 through 7.0.6000.16473 contain a vulnerability that enables remote attackers to perform a denial of service attack by consuming excessive CPU resources. This flaw specifically occurs when processing XML documents that contain an extended sequence of start-tags without corresponding end-tags, creating an infinite parsing loop that consumes system resources and potentially crashes the browser application.
The vulnerability stems from inadequate input validation and parsing logic within the XML parser component of Internet Explorer. When the browser encounters malformed XML containing numerous unclosed start-tags, the parser enters a recursive or iterative processing state that fails to properly terminate execution. This behavior represents a classic example of a resource exhaustion attack where malicious actors can craft XML documents designed to maximize CPU utilization while minimizing memory consumption, effectively creating a denial of service condition that impacts system performance and availability.
From a cybersecurity perspective, this vulnerability aligns with CWE-400, which categorizes "Uncontrolled Resource Consumption" as a significant weakness in software systems. The attack vector operates through the browser's XML processing capabilities, making it particularly dangerous as it can be triggered through standard web browsing activities without requiring special privileges or complex exploitation techniques. The related vulnerability CVE-2009-1232 demonstrates similar patterns of resource exhaustion through XML parsing flaws, indicating a broader class of issues affecting Internet Explorer's XML handling mechanisms.
The operational impact of this vulnerability extends beyond simple browser instability, as it can be leveraged to disrupt user productivity and potentially serve as a stepping stone for more sophisticated attacks. Attackers can craft malicious web pages or documents that, when opened in affected browsers, cause continuous CPU spikes that may render the system unresponsive or force application crashes. This type of attack can be particularly effective in enterprise environments where users may inadvertently access compromised websites or documents, leading to widespread service disruption.
Mitigation strategies for this vulnerability should include immediate deployment of Microsoft security updates and patches that address the XML parsing logic flaws. Organizations should implement network-level controls to filter potentially malicious XML content and consider browser hardening measures such as disabling automatic XML processing or implementing content security policies. Additionally, user education regarding the risks of accessing untrusted web content and the importance of keeping software updated remains crucial in preventing exploitation. The ATT&CK framework categorizes this type of vulnerability under T1499, which covers "Network Denial of Service" techniques, emphasizing the need for both defensive and detection measures to protect against resource exhaustion attacks targeting browser components.