CVE-2016-9623 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.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 10/05/2022
The vulnerability identified as CVE-2016-9623 affects the w3m web browser fork developed by Tatsuya Kinoshita, specifically versions prior to 0.5.3-33. This issue represents a denial of service vulnerability that can be exploited by remote attackers through the manipulation of HTML content, potentially causing the application to crash with a segmentation fault. The w3m browser, known for its text-based interface and lightweight design, is widely used in environments where graphical browsers are not available or practical. The vulnerability stems from inadequate input validation and memory management within the HTML parsing component of the browser, creating an exploitable condition that allows attackers to craft malicious HTML pages designed to trigger the crash.
The technical flaw manifests when the w3m browser encounters specifically crafted HTML content that causes memory corruption during the parsing process. This type of vulnerability falls under the category of memory safety issues and can be classified as a CWE-125: Out-of-bounds Read or CWE-787: Out-of-bounds Write depending on the exact execution path. The segmentation fault occurs when the browser attempts to access memory locations that are either invalid or unauthorized, leading to an abrupt termination of the application. The vulnerability is particularly concerning because it requires no authentication or privileged access from the attacker, making it a remote code execution risk that can be exploited through web-based attacks. The attack vector involves the delivery of malicious HTML content through standard web browsing channels, where a user's browser would automatically attempt to render the content, triggering the vulnerable code path.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be leveraged in various attack scenarios including web-based phishing campaigns, malicious website redirections, and targeted attacks against users who rely on w3m for their browsing needs. Organizations that deploy w3m in restricted environments or embedded systems may find their operational continuity compromised, as the crash can occur without warning and potentially lead to data loss or service unavailability. The vulnerability affects both desktop and server environments where w3m is used as a browser component, particularly in scenarios where automated content rendering is expected. From an attack perspective, this vulnerability aligns with ATT&CK technique T1203: Exploitation for Client Execution, where adversaries leverage application vulnerabilities to execute malicious code or cause system instability. The remote nature of the attack means that users can be compromised simply by visiting a malicious website, making it particularly dangerous in environments where users have limited security awareness.
Mitigation strategies for this vulnerability primarily involve updating to w3m version 0.5.3-33 or later, which includes patches addressing the memory handling issues in HTML parsing. System administrators should implement immediate patch management procedures to ensure all affected installations are updated promptly. Additional protective measures include implementing web content filtering solutions that can detect and block known malicious HTML patterns, as well as deploying network-based intrusion detection systems that can monitor for exploitation attempts. The vulnerability also highlights the importance of input sanitization and robust memory management practices in browser implementations, which aligns with security best practices outlined in the OWASP Top Ten and NIST cybersecurity guidelines. Organizations should also consider implementing application whitelisting policies that restrict the execution of untrusted web content, particularly in high-security environments where the risk of exploitation is elevated. Regular security assessments and vulnerability scanning should be conducted to identify similar issues in other browser implementations or web-based applications that may present similar attack surfaces.