CVE-2016-9432 in w3m
Summary
by MITRE
An issue was discovered in the Tatsuya Kinoshita w3m fork before 0.5.3-31. w3m allows remote attackers to cause a denial of service (memory corruption, segmentation fault, and crash) via a crafted HTML page.
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Analysis
by VulDB Data Team • 10/05/2022
The vulnerability identified as CVE-2016-9432 represents a critical memory corruption flaw within the w3m web browser fork developed by Tatsuya Kinoshita. This issue affects versions prior to 0.5.3-31 and demonstrates how seemingly benign web content can be weaponized to disrupt system operations. The w3m browser, known for its lightweight design and terminal-based interface, is widely used in environments where resource constraints are significant, making this vulnerability particularly concerning for embedded systems and server deployments.
The technical nature of this flaw stems from inadequate input validation and memory management within the HTML parsing component of the w3m browser. When processing a specially crafted HTML page, the browser fails to properly handle malformed or maliciously constructed elements, leading to memory corruption that ultimately results in segmentation faults and system crashes. This type of vulnerability falls under the CWE-121 category of "Stack-based Buffer Overflow" and aligns with ATT&CK technique T1499.004 for Network Denial of Service. The memory corruption occurs during the rendering process when the browser attempts to parse and display elements that exceed expected parameter boundaries, causing the application to behave unpredictably and terminate abruptly.
From an operational perspective, this vulnerability creates significant risk for organizations relying on w3m for web browsing in constrained environments. The denial of service impact extends beyond simple browser disruption, as it can affect automated systems that depend on consistent browser functionality for web scraping, monitoring, or content delivery tasks. Attackers can exploit this vulnerability remotely without requiring authentication, making it particularly dangerous in public or shared network environments where users might encounter malicious web content. The vulnerability's exploitation requires minimal technical expertise, as it only necessitates the delivery of a crafted HTML page to trigger the memory corruption and subsequent crash.
Mitigation strategies for CVE-2016-9432 primarily focus on immediate software updates to versions 0.5.3-31 or later, which contain the necessary patches to address the memory handling flaws. Organizations should also implement network-level controls such as web content filtering and HTML sanitization to prevent access to potentially malicious pages. Additionally, system administrators should consider implementing application sandboxing or containerization for w3m instances to limit the potential impact of successful exploitation attempts. The vulnerability highlights the importance of regular security updates and proper input validation in browser implementations, particularly for lightweight applications that may not receive the same level of security scrutiny as mainstream browsers. Organizations using w3m should also conduct thorough security assessments of their web browsing environments to identify and remediate similar vulnerabilities that may exist in other components of their systems.