CVE-2016-9437 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) and possibly memory corruption via a crafted HTML page.
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Analysis
by VulDB Data Team • 10/05/2022
The vulnerability identified as CVE-2016-9437 affects the w3m web browser fork developed by Tatsuya Kinoshita and represents a critical security flaw that can be exploited remotely to cause system instability. This issue exists in versions prior to 0.5.3-31 of the software, making it a significant concern for users who rely on this lightweight terminal-based browser for web navigation. The vulnerability manifests as a segmentation fault and subsequent crash, which can be triggered by presenting a specially crafted HTML page to an unsuspecting user. The flaw demonstrates the inherent risks associated with parsing malformed web content in terminal-based browsers that lack comprehensive input validation mechanisms.
The technical nature of this vulnerability stems from insufficient input sanitization within the w3m browser's HTML parsing engine, which fails to properly handle malformed or maliciously constructed HTML elements. When processing a crafted HTML page, the browser's rendering engine encounters unexpected data structures that cause memory access violations, leading to segmentation faults and system crashes. This type of vulnerability falls under the CWE-121 category of Stack-based Buffer Overflow, though it manifests more broadly as a general memory corruption issue that can be exploited through improper input handling. The flaw represents a classic example of how insufficient bounds checking and input validation can lead to system instability and potential remote code execution scenarios.
The operational impact of CVE-2016-9437 extends beyond simple denial of service conditions, as it can potentially enable attackers to cause memory corruption that might be leveraged for more sophisticated attacks. In environments where w3m is used for automated browsing or as part of larger security toolchains, this vulnerability could be exploited to disrupt services or potentially escalate privileges. The vulnerability's remote exploitability means that attackers do not need physical access to the target system, allowing them to compromise devices simply by enticing users to visit malicious websites or receive crafted web content through other attack vectors. This makes the vulnerability particularly dangerous in enterprise environments where users may inadvertently encounter malicious content through phishing campaigns or compromised websites.
Organizations and users affected by this vulnerability should immediately upgrade to w3m version 0.5.3-31 or later, which includes patches addressing the HTML parsing flaws that lead to the segmentation faults and memory corruption issues. System administrators should implement network-level controls to block access to known malicious domains and consider deploying web application firewalls that can detect and prevent the delivery of crafted HTML content. Additionally, users should be educated about the risks of visiting untrusted websites and should avoid clicking on suspicious links or downloading content from unknown sources. The vulnerability demonstrates the importance of keeping terminal-based browsers updated and highlights the need for comprehensive input validation in all web rendering components, aligning with ATT&CK techniques that focus on privilege escalation and execution through compromised applications. Regular security assessments and vulnerability scanning should be implemented to identify similar issues in other browser implementations and ensure that all components of the web browsing stack maintain adequate security controls.