CVE-2016-9424 in w3m
Summary
by MITRE
An issue was discovered in the Tatsuya Kinoshita w3m fork before 0.5.3-31. w3m doesn't properly validate the value of tag attribute, which allows remote attackers to cause a denial of service (heap buffer overflow crash) and possibly execute arbitrary code via a crafted HTML page.
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Analysis
by VulDB Data Team • 10/05/2022
The vulnerability identified as CVE-2016-9424 affects the w3m web browser fork developed by Tatsuya Kinoshita, specifically versions prior to 0.5.3-31. This issue represents a critical security flaw that demonstrates poor input validation practices within the HTML parsing component of the browser. The vulnerability manifests when the w3m application processes HTML content containing malformed tag attributes, creating a scenario where malicious actors can exploit the software's inadequate sanitization mechanisms to compromise system integrity.
The technical root cause of this vulnerability lies in the improper validation of tag attribute values within the w3m browser's HTML processing engine. When encountering crafted HTML content with malformed attributes, the application fails to properly bounds-check memory allocations, leading to a heap buffer overflow condition. This type of vulnerability falls under the CWE-121 heap-based buffer overflow category, where insufficient validation of user-supplied input allows attackers to write beyond allocated memory boundaries. The flaw specifically targets the memory management routines responsible for handling HTML tag attributes, creating a condition where arbitrary memory locations can be overwritten or accessed.
From an operational perspective, this vulnerability presents significant risks to users of affected w3m versions, as it can be exploited through simple web page delivery without requiring any special privileges or user interaction beyond normal browsing. The potential impact extends beyond mere denial of service, as the heap buffer overflow condition could potentially be leveraged to execute arbitrary code on the target system. This represents a classic remote code execution vulnerability that aligns with ATT&CK technique T1203, where adversaries exploit software vulnerabilities to gain execution capabilities. The vulnerability's exploitation requires only a maliciously crafted HTML page, making it particularly dangerous in environments where users may encounter untrusted web content.
The security implications of CVE-2016-9424 extend to various threat actor categories including automated malware scanners, targeted attackers, and malicious website operators. Attackers could craft HTML pages specifically designed to trigger this buffer overflow, potentially allowing them to execute malicious payloads or establish persistent access to compromised systems. The vulnerability's presence in a widely used terminal-based web browser increases its attack surface significantly, as it affects users across various operating systems and environments where w3m is deployed. Organizations and individuals using affected versions should immediately implement mitigation strategies including software updates, web filtering measures, and user education to prevent exploitation attempts.
Mitigation strategies for this vulnerability primarily focus on immediate software patching to version 0.5.3-31 or later, which incorporates proper input validation and bounds-checking mechanisms. Additionally, system administrators should implement network-based filtering to block access to known malicious web content and consider deploying web application firewalls to monitor and filter potentially harmful HTML content. The vulnerability also highlights the importance of proper memory management practices in software development, emphasizing the need for comprehensive input validation and bounds checking as outlined in secure coding standards and best practices. Organizations should conduct vulnerability assessments to identify all systems running affected w3m versions and ensure proper patch management procedures are in place to prevent similar issues from occurring in the future.