CVE-2016-9632 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 (global buffer overflow and crash) via a crafted HTML page.
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Analysis
by VulDB Data Team • 09/17/2024
The vulnerability identified as CVE-2016-9632 represents a critical buffer overflow flaw within the w3m web browser implementation developed by Tatsuya Kinoshita. This issue affects versions prior to 0.5.3-33 and demonstrates how seemingly innocuous web content can be weaponized to disrupt system operations. The w3m browser, known for its lightweight design and terminal-based interface, is widely used in environments where resource constraints are a primary concern, making this vulnerability particularly concerning for embedded systems and server deployments. The flaw specifically manifests when the browser processes crafted HTML content that triggers an improper memory handling mechanism, leading to a global buffer overflow condition that ultimately results in application crash.
The technical exploitation of this vulnerability occurs through the manipulation of HTML parsing routines within the w3m fork. When the browser encounters specially crafted HTML elements or attributes, the parsing engine fails to properly validate input boundaries, allowing malicious data to overflow predetermined buffer limits. This buffer overflow condition affects global memory structures rather than local variables, which amplifies the severity and impact of the flaw. The vulnerability stems from inadequate bounds checking during HTML content rendering, particularly when processing complex nested elements or malformed markup structures. According to CWE classification, this represents a variant of CWE-121, heap-based buffer overflow, though specifically manifested in a global buffer context that makes exploitation more predictable and reliable.
The operational impact of CVE-2016-9632 extends beyond simple denial of service, as it can be leveraged to disrupt critical services in environments where w3m is deployed. System administrators and security professionals must consider the broader implications of this vulnerability in contexts such as automated web scraping applications, terminal-based email clients, or embedded devices that rely on w3m for web content display. The crash condition can be reliably triggered through web-based attacks, making it a potential vector for persistent denial of service campaigns against systems that depend on this browser component. From an ATT&CK framework perspective, this vulnerability aligns with the T1499.004 technique for network denial of service, as it specifically targets application stability through memory corruption. The vulnerability also relates to T1595.001 reconnaissance activities, as attackers can use this flaw to identify systems running vulnerable versions of w3m.
Mitigation strategies for CVE-2016-9632 primarily focus on immediate version updates to w3m 0.5.3-33 or later, which contain the necessary patches to address the buffer overflow condition. System administrators should conduct comprehensive vulnerability assessments to identify all systems running affected w3m versions, particularly those deployed in server environments or critical infrastructure. Additional protective measures include implementing web content filtering mechanisms that can detect and block suspicious HTML content, as well as monitoring network traffic for patterns indicative of exploitation attempts. The vulnerability highlights the importance of maintaining up-to-date software libraries and the necessity of thorough input validation in web browser implementations. Organizations should also consider implementing sandboxing techniques or containerization strategies to limit the potential impact of such vulnerabilities in production environments. Regular security audits and penetration testing should include verification of w3m installations to ensure that patched versions are properly deployed across all affected systems.