CVE-2016-9633 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 (infinite loop and resource consumption) via a crafted HTML page.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 09/17/2024
The vulnerability identified as CVE-2016-9633 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, contains a processing error that can be exploited by remote attackers to consume excessive system resources and potentially cause system instability. The vulnerability affects versions prior to 0.5.3-33, indicating that this was a specific issue within the software development lifecycle that was subsequently addressed through version updates.
The technical flaw manifests through improper handling of malformed HTML content during the parsing and rendering process. When a crafted HTML page is processed by the vulnerable w3m implementation, the browser enters an infinite loop during the parsing phase, causing continuous resource consumption without termination. This behavior stems from inadequate input validation and error handling mechanisms within the HTML parser component of the browser. The infinite loop occurs when the parser encounters specific HTML constructs that trigger recursive processing without proper termination conditions, leading to unbounded CPU usage and memory consumption that can exhaust system resources.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise system availability and performance. Remote attackers can leverage this vulnerability to perform denial of service attacks against systems running vulnerable w3m versions, causing legitimate users to lose access to web browsing capabilities. The resource exhaustion can lead to system instability, particularly on systems with limited computational resources or when multiple instances of the browser are running simultaneously. This type of vulnerability is particularly concerning in environments where w3m is used as a default browser or in automated systems where availability is critical.
This vulnerability aligns with CWE-835, which describes the weakness of infinite loops or infinite recursion in software implementations. The attack pattern corresponds to the ATT&CK technique T1499.004, which involves network denial of service attacks through resource exhaustion. The flaw demonstrates poor input validation practices and inadequate error handling in web browser implementations, highlighting the importance of robust parsing mechanisms in text-based browsers. Organizations should implement immediate mitigation strategies including updating to patched versions of w3m, implementing network-level filtering to block suspicious HTML content, and monitoring for unusual resource consumption patterns that may indicate exploitation attempts. The vulnerability also underscores the need for comprehensive security testing of parsing components in web browsers and the importance of maintaining current software versions to protect against known vulnerabilities.