CVE-2016-9631 in w3m
Summary
by MITRE
An issue was discovered in the Tatsuya Kinoshita w3m fork before 0.5.3-33. 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 • 09/17/2024
The vulnerability identified as CVE-2016-9631 represents a critical denial of service flaw within the w3m web browser implementation developed by Tatsuya Kinoshita. This particular version of the w3m fork, specifically prior to 0.5.3-33, exhibits a susceptibility that can be exploited by remote attackers to induce system crashes through the manipulation of HTML content. The affected software demonstrates a failure in proper input validation and memory management when processing malformed HTML documents, creating an exploitable condition that fundamentally undermines the stability and availability of the application. This vulnerability falls under the category of software quality assurance failures where insufficient boundary checking and error handling mechanisms allow malicious input to trigger unexpected program termination.
The technical nature of this flaw stems from inadequate parsing and handling of HTML elements within the w3m browser's rendering engine. When a crafted HTML page containing malformed or specially constructed elements is processed by the vulnerable version, the application encounters a segmentation fault during memory access operations. This occurs because the browser fails to properly validate the structure and content of HTML tags, particularly when encountering unexpected sequences or malformed attributes that exceed buffer boundaries. The vulnerability manifests as a direct result of insufficient bounds checking in the HTML parser component, which is classified as a CWE-121 heap-based buffer overflow or CWE-129 improper input validation. The segmentation fault triggers a crash that terminates the application process, effectively rendering the browser unavailable to legitimate users and creating a denial of service condition that can be remotely exploited.
The operational impact of CVE-2016-9631 extends beyond simple application instability to encompass broader security implications for systems that rely on w3m for web content viewing or automated processing. Remote attackers can leverage this vulnerability to disrupt services by simply presenting a maliciously crafted HTML page to a victim's browser, requiring no special privileges or complex attack vectors. This makes the vulnerability particularly dangerous in environments where w3m is used for automated content retrieval, web scraping, or as part of larger security monitoring systems. The vulnerability can be exploited across different network environments and operating systems where the affected w3m version is deployed, creating widespread potential for service disruption. From an adversarial perspective, this flaw aligns with ATT&CK technique T1499.004 which involves network denial of service attacks, and demonstrates how seemingly benign web content can be weaponized to compromise system availability.
Mitigation strategies for this vulnerability require immediate software updates to versions 0.5.3-33 or later where the parsing and input validation mechanisms have been corrected. System administrators should prioritize patching affected installations and implement network monitoring to detect potential exploitation attempts. Additional protective measures include deploying web content filtering solutions that can identify and block suspicious HTML content before it reaches vulnerable applications, as well as implementing application sandboxing techniques that limit the impact of potential crashes. Organizations should also consider implementing automated vulnerability scanning processes that can identify systems running vulnerable versions of w3m and prioritize remediation efforts accordingly. The fix for this vulnerability typically involves strengthening input validation routines, implementing proper memory management practices, and adding comprehensive error handling to prevent malformed HTML content from causing segmentation faults. Security teams should monitor for any related vulnerabilities in the w3m codebase and maintain updated threat intelligence on similar parsing flaws that could affect other browser implementations or web-based applications.