CVE-2016-9630 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 • 09/16/2024
The vulnerability identified as CVE-2016-9630 represents a critical buffer overflow flaw within the w3m web browser fork developed by Tatsuya Kinoshita. This issue affects versions prior to 0.5.3-33 and demonstrates a classic security weakness that can be exploited by remote attackers to disrupt system operations. The w3m browser, known for its lightweight design and text-based interface, is widely used in environments where graphical browsers are not available or desired. The vulnerability specifically manifests as a global buffer overflow when processing crafted HTML content, creating a scenario where attacker-controlled input can overwrite adjacent memory regions beyond the intended buffer boundaries.
The technical nature of this flaw falls under the category of CWE-121, which describes stack-based buffer overflow conditions, and more specifically relates to CWE-787, which addresses out-of-bounds write operations. When a malicious HTML page is loaded through the vulnerable w3m implementation, the browser fails to properly validate input length and memory allocation during HTML parsing. This allows an attacker to craft HTML content that, when rendered, triggers memory corruption patterns leading to unpredictable behavior and system instability. The global buffer overflow occurs because the application does not perform adequate bounds checking on user-supplied data, particularly in HTML element handling routines that process potentially malicious content.
From an operational perspective, this vulnerability presents significant risks to users who rely on w3m for web browsing, particularly in environments where automated security updates are not consistently applied. The denial of service impact means that a single malicious webpage can cause the browser to crash and terminate unexpectedly, potentially leading to loss of unsaved work or interrupted browsing sessions. In more severe scenarios, attackers could potentially leverage this vulnerability to execute arbitrary code through memory corruption techniques, though the immediate impact is primarily focused on service disruption. The remote exploitability aspect means that users do not need physical access to the target system, making this vulnerability particularly concerning for environments where users may encounter untrusted web content.
Organizations and individual users should prioritize immediate remediation by upgrading to w3m version 0.5.3-33 or later, which includes proper bounds checking and memory management fixes. System administrators should also implement network-level protections such as web application firewalls and content filtering solutions to prevent access to known malicious domains. The vulnerability aligns with ATT&CK technique T1203, which describes exploitation of software vulnerabilities for privilege escalation or system compromise. Additionally, this flaw demonstrates the importance of input validation and memory safety practices in software development, particularly for applications that process untrusted data from web sources. Regular security assessments and vulnerability scanning should be conducted to identify similar issues in other browser implementations or web-based applications that may be susceptible to similar buffer overflow conditions.