CVE-2009-1335 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 7 and 8 on Windows XP and Vista allows remote attackers to cause a denial of service (application hang) via a large document composed of unprintable characters, aka MSRC 9011jr.
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Analysis
by VulDB Data Team • 10/01/2025
Microsoft Internet Explorer 7 and 8 versions contain a critical vulnerability that enables remote attackers to trigger a denial of service condition through carefully crafted malicious documents. This vulnerability specifically affects systems running Windows XP and Vista operating systems, making it particularly concerning given the widespread deployment of these platforms. The flaw manifests when the browser encounters a document containing an excessive number of unprintable characters, causing the application to become unresponsive and eventually hang. This behavior represents a classic buffer overflow scenario where the browser's rendering engine fails to properly handle malformed input data. The vulnerability falls under the category of improper input validation as defined by CWE-20, where the application does not adequately sanitize or limit the size and content of incoming data streams. From an operational perspective, this vulnerability creates significant risk for organizations relying on these older browser versions, as attackers can remotely disrupt user productivity and system availability. The attack vector is particularly dangerous because it requires no special privileges or authentication, making it accessible to any remote user who can deliver the malicious content to a targeted system. This vulnerability maps directly to the ATT&CK technique T1499.004 which covers network denial of service attacks. The technical implementation involves the browser's HTML rendering engine encountering excessive whitespace or control characters that cause memory allocation issues within the application's memory management subsystem. When the rendering process attempts to process these malformed documents, the application's memory consumption spikes dramatically, leading to the application hang condition. The impact extends beyond simple service disruption as users may experience complete browser crashes requiring manual restart of the application. Organizations running these vulnerable versions face increased risk of operational downtime and potential productivity losses. The vulnerability demonstrates the importance of proper input sanitization and memory management practices in web browser implementations. Security researchers have noted that this type of vulnerability often indicates deeper architectural issues within the browser's parsing and rendering components. The lack of adequate bounds checking in the document processing pipeline allows attackers to exploit memory handling weaknesses. This vulnerability highlights the ongoing challenges in maintaining secure browser implementations, particularly for legacy software versions that may not receive regular security updates. The issue represents a fundamental flaw in how the browser handles edge cases in document parsing, exposing systems to potential exploitation by malicious actors. Organizations should prioritize immediate mitigation through browser updates or patches, as the vulnerability provides no legitimate use case for the targeted functionality. The flaw underscores the necessity of implementing robust input validation mechanisms and proper error handling within application code. Without adequate protection against malformed input, browsers remain vulnerable to various forms of denial of service attacks that can severely impact operational continuity. This vulnerability serves as a reminder of the critical importance of maintaining up-to-date software implementations and the risks associated with running unsupported browser versions in enterprise environments. The technical nature of the flaw suggests that similar vulnerabilities may exist in other components of the browser architecture, emphasizing the need for comprehensive security assessments. Proper mitigation requires not only patching the specific vulnerability but also implementing network-level protections and user education regarding safe browsing practices. The vulnerability's classification as a denial of service issue indicates that attackers can leverage it to disrupt normal business operations and potentially create conditions for more sophisticated attacks. Organizations should consider implementing additional security controls such as web application firewalls and browser security policies to reduce exposure to this and similar threats. The presence of such vulnerabilities in widely deployed software underscores the importance of continuous security monitoring and rapid response capabilities within enterprise security programs.