CVE-2016-9628 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 • 10/05/2022
The vulnerability identified as CVE-2016-9628 represents a critical denial of service flaw within the w3m web browser implementation developed by Tatsuya Kinoshita. This particular fork of the w3m browser, which is a text-based web browser designed for terminal environments, was found to be susceptible to remote exploitation through specially crafted HTML content that could trigger segmentation faults and subsequent system crashes. The vulnerability specifically affects versions prior to 0.5.3-33, indicating that the issue was present in the software development lineage leading up to that particular release. The w3m browser, being widely used in environments where graphical user interfaces are unavailable or impractical, such as servers, embedded systems, and terminal-based computing environments, made this vulnerability particularly concerning for system administrators and security professionals managing such platforms.
The technical nature of this flaw stems from inadequate input validation and memory handling within the HTML parsing mechanisms of the w3m browser. When processing maliciously constructed HTML pages, the browser fails to properly validate or sanitize input data, leading to memory corruption that manifests as segmentation faults during rendering operations. This type of vulnerability falls under the category of buffer overflows or memory corruption issues that are commonly classified under CWE-121, which deals with stack-based buffer overflow conditions. The exploitation process requires remote attackers to craft specific HTML content that, when loaded by the vulnerable w3m instance, causes the browser to access invalid memory locations or manipulate memory in unintended ways, resulting in system crashes and service unavailability.
The operational impact of CVE-2016-9628 extends beyond simple service disruption as it affects systems where w3m serves as a primary or secondary web browsing mechanism. In server environments, particularly those running headless systems or embedded devices that rely on text-based browsers for web interactions, a successful exploitation could lead to complete service outages and potential compromise of system availability. The vulnerability's remote nature means that attackers do not require physical access or local privileges to exploit the flaw, making it particularly dangerous in publicly accessible environments. Organizations using w3m in production systems, including those in the Internet of Things deployments, cloud computing environments, or restricted terminal access scenarios, would face significant operational risks if they remained vulnerable to this denial of service condition. The attack vector through HTML content exploitation aligns with common attack patterns documented in the ATT&CK framework under the Tactic of Execution, specifically targeting applications through malicious input manipulation.
The mitigation strategy for CVE-2016-9628 centers on immediate software updates to versions 0.5.3-33 or later, which contain the necessary patches to address the memory handling and input validation deficiencies. System administrators should prioritize patching affected w3m installations across all environments where the browser is deployed, particularly in server and embedded systems where the impact of service disruption would be most significant. Additional defensive measures include implementing network-level filtering to restrict access to potentially malicious HTML content, deploying intrusion detection systems to monitor for exploitation attempts, and considering the deployment of alternative browser solutions where appropriate. The vulnerability serves as a reminder of the importance of maintaining current software versions and implementing robust input validation mechanisms in applications that process untrusted data, aligning with security best practices outlined in various cybersecurity frameworks including NIST SP 800-160 and ISO/IEC 27001 standards for secure software development practices.