CVE-2016-9443 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.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 10/05/2022
The vulnerability identified as CVE-2016-9443 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 enables remote attackers to crash the application through manipulation of HTML content. The vulnerability manifests as a segmentation fault during HTML parsing, leading to application instability and potential system disruption. The w3m browser, known for its text-based interface and lightweight design, is widely used in environments where graphical browsers are not available or practical. The flaw exists within the HTML parsing engine, specifically in how the application handles malformed or crafted HTML structures. Attackers can exploit this vulnerability by crafting malicious HTML pages that trigger memory access violations when processed by the vulnerable w3m version. This issue falls under the category of software quality and security assurance, where improper input validation leads to application instability.
The technical implementation of this vulnerability stems from inadequate bounds checking and memory management within the HTML parser component of w3m. When processing crafted HTML content, the parser fails to properly validate input parameters, leading to buffer overflows or invalid memory access patterns that result in segmentation faults. The flaw is classified as a buffer overflow vulnerability under CWE-121, which specifically addresses issues related to insufficient space for buffers. The vulnerability operates at the application layer and can be exploited through web-based delivery methods, making it particularly dangerous in environments where users might encounter malicious content. The segmentation fault occurs during the parsing phase when the application attempts to access memory locations that are either invalid or protected, causing an abrupt termination of the process. This type of vulnerability is commonly associated with memory corruption issues that can be exploited to cause system instability or potentially enable more sophisticated attacks.
The operational impact of CVE-2016-9443 extends beyond simple service disruption to encompass potential system reliability concerns. Organizations relying on w3m for terminal-based browsing or automated systems may experience unexpected application crashes, leading to service interruptions and user frustration. The vulnerability can be exploited in various scenarios including web browsing sessions, automated content delivery systems, and environments where w3m is integrated into larger applications. Attackers can leverage this weakness to perform DoS attacks against systems using vulnerable w3m versions, potentially affecting availability of information services. The vulnerability also aligns with ATT&CK technique T1499.004, which covers network denial of service attacks through application-level exploitation. In enterprise environments, this could compromise access to information systems, particularly in contexts where w3m is used for automated data retrieval or system monitoring functions.
Mitigation strategies for CVE-2016-9443 primarily involve upgrading to w3m version 0.5.3-31 or later, which includes patches addressing the HTML parsing vulnerabilities. System administrators should implement regular patch management protocols to ensure all installations remain current with security updates. Additional protective measures include implementing web filtering solutions that can block suspicious HTML content before it reaches vulnerable applications, and establishing network segmentation to limit exposure. Organizations should also consider implementing application whitelisting policies that restrict execution of untrusted HTML content through w3m. The vulnerability highlights the importance of input validation and proper memory management in security-critical applications, aligning with security best practices outlined in NIST SP 800-160 and ISO 27001 standards. Regular security assessments and penetration testing should be conducted to identify similar vulnerabilities in other applications within the system landscape. Furthermore, developers should follow secure coding practices that emphasize robust error handling and memory safety mechanisms to prevent similar issues in future implementations.