CVE-2016-9438 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-2016-9438 affects the w3m web browser fork developed by Tatsuya Kinoshita, specifically versions prior to 0.5.3-31. This issue represents a classic buffer overflow condition that manifests as a segmentation fault, leading to application crash and potential denial of service. The vulnerability arises from insufficient input validation and memory management within the HTML parsing component of the browser, creating a scenario where maliciously crafted HTML content can trigger unexpected behavior in the application's execution flow. The affected w3m fork represents a widely used text-based web browser that operates in terminal environments, making it particularly relevant for system administrators and security professionals managing terminal-based access points.
The technical flaw stems from improper handling of malformed HTML structures within the w3m rendering engine, specifically when processing certain HTML tags or attributes that exceed expected memory boundaries. When the browser encounters crafted HTML content containing oversized or malformed elements, the parsing routine fails to properly validate input parameters before attempting memory allocation or manipulation operations. This condition creates a scenario where the application attempts to access memory locations outside of its allocated address space, resulting in a segmentation fault that terminates the process. The vulnerability operates at the application layer and requires user interaction through the viewing of maliciously crafted web content, making it a remote attack vector that can be exploited through web-based delivery mechanisms.
The operational impact of this vulnerability extends beyond simple application instability, as it can be leveraged by remote attackers to disrupt legitimate user access to web content and potentially create service availability issues. In environments where w3m is used for terminal-based browsing or automated access, such as kiosks, embedded systems, or remote administration interfaces, this vulnerability can significantly compromise system availability and user productivity. The denial of service effect can be particularly problematic in critical infrastructure scenarios where terminal-based access is the primary means of system interaction, as attackers can effectively prevent legitimate users from accessing web resources. This vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and represents a common class of memory corruption vulnerabilities that can lead to both denial of service and potential privilege escalation scenarios.
Mitigation strategies for CVE-2016-9438 should prioritize immediate patch deployment to version 0.5.3-31 or later, as this addresses the core memory handling issues within the HTML parser. System administrators should implement network-level filtering to prevent access to untrusted web content when direct patching is not immediately feasible, particularly in environments where w3m is actively used for browser access. Additional protective measures include implementing application sandboxing techniques to limit the impact of potential exploitation, deploying intrusion detection systems to monitor for suspicious HTML content patterns, and establishing regular security assessments of terminal-based browsing environments. The vulnerability also highlights the importance of maintaining updated software versions and implementing proper input validation procedures, as outlined in the ATT&CK framework's defense-in-depth strategies for application security. Organizations should consider implementing automated patch management processes to ensure timely deployment of security updates, particularly for widely used terminal-based applications that may be targeted by adversaries seeking to exploit availability vulnerabilities.