CVE-2016-9441 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 (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-2016-9441 affects the w3m web browser fork developed by Tatsuya Kinoshita, specifically versions prior to 0.5.3-31. This represents a critical denial of service flaw that can be exploited by remote attackers to crash the application through maliciously crafted HTML content. The vulnerability manifests as a segmentation fault, causing the browser to terminate unexpectedly and potentially disrupting user sessions. The affected software is a text-based web browser designed for terminal environments, commonly used in constrained system environments or for accessibility purposes. This type of vulnerability is particularly concerning in environments where uninterrupted access to web content is critical, as it can be leveraged to disrupt services or create availability issues for legitimate users.
The technical root cause of this vulnerability lies in inadequate input validation within the HTML parsing mechanisms of the w3m browser. When processing specially crafted HTML pages, the application fails to properly handle malformed or unexpected HTML structures, leading to memory access violations that result in segmentation faults. This flaw demonstrates poor error handling and memory management practices during HTML content rendering, where the parser does not adequately check boundaries or validate the structure of incoming HTML elements before attempting to process them. The vulnerability is classified under CWE-125 as an out-of-bounds read, which occurs when the application attempts to access memory beyond the allocated buffer boundaries during HTML parsing operations. This type of memory corruption vulnerability can potentially be exploited beyond simple denial of service to achieve more severe consequences if additional flaws exist in the memory management subsystem.
The operational impact of CVE-2016-9441 extends beyond simple service disruption to potentially compromise user productivity and system availability. In environments where w3m is used for automated browsing tasks, web scraping, or as part of larger system workflows, a successful exploitation could result in cascading failures that affect multiple dependent processes. Users may experience unexpected browser crashes while navigating to legitimate websites, leading to data loss or interrupted work sessions. The vulnerability is particularly dangerous in scenarios where w3m is integrated into larger applications or systems, as the crash could propagate through application layers and potentially expose the system to additional attack vectors. From an attacker's perspective, this vulnerability represents a low-effort, high-impact method for service disruption that requires minimal technical expertise to exploit.
Mitigation strategies for CVE-2016-9441 primarily focus on immediate software updates and input validation improvements. Organizations should prioritize upgrading to w3m version 0.5.3-31 or later, which contains the necessary patches to address the HTML parsing vulnerabilities. System administrators should implement network-level controls to filter potentially malicious content when w3m is used in public or untrusted environments. The vulnerability aligns with ATT&CK technique T1499.004 for network denial of service, where attackers exploit application-level vulnerabilities to disrupt services. Additional defensive measures include implementing sandboxing techniques to limit the impact of potential crashes, deploying intrusion detection systems to monitor for exploitation attempts, and establishing robust application monitoring to quickly identify and respond to service disruptions. Regular security assessments of text-based browsers and terminal applications should be conducted to identify similar vulnerabilities in other components of the system infrastructure.