CVE-2016-9622 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-2016-9622 affects the w3m web browser fork developed by Tatsuya Kinoshita, specifically versions prior to 0.5.3-33. This issue represents a classic denial of service vulnerability that can be exploited by remote attackers to crash the application through the careful crafting of HTML content. The w3m browser, known for its lightweight design and text-based interface, is widely used in environments where graphical browsers are not available or desirable. The vulnerability manifests as a segmentation fault that leads to an application crash, effectively rendering the browser unusable for the duration of the attack.
The technical flaw stems from inadequate input validation within the HTML parsing functionality of the w3m browser. When processing maliciously crafted HTML pages, the parser fails to properly handle certain malformed or specially constructed elements, leading to memory access violations that trigger segmentation faults. This type of vulnerability falls under CWE-121, which encompasses buffer overflow conditions, and more specifically aligns with CWE-125, which deals with out-of-bounds read errors. The vulnerability operates at the application layer, making it particularly dangerous as it requires no special privileges or local access to exploit. Attackers can simply host a malicious HTML page and persuade victims to view it through the vulnerable w3m browser, making this a remote attack vector that can be executed through web browsing activities.
The operational impact of this vulnerability extends beyond simple service disruption. Organizations that rely on w3m for automated browsing tasks, system administration, or embedded environments may experience unexpected application failures that could compromise system stability. In enterprise settings where w3m is used for web-based monitoring or automated data retrieval, a successful exploitation could lead to intermittent service outages or data collection failures. The vulnerability also represents a potential vector for more sophisticated attacks, as the crash conditions could be leveraged to execute other exploits or serve as a stepping stone for further compromise. From an attacker perspective, this vulnerability aligns with ATT&CK technique T1499.004, which covers the use of application or system exploitation to cause denial of service, and demonstrates how seemingly benign web browsing activities can become attack vectors.
Mitigation strategies for CVE-2016-9622 primarily focus on upgrading to patched versions of the w3m browser, specifically versions 0.5.3-33 or later. System administrators should implement regular patch management procedures to ensure all instances of the vulnerable software are updated promptly. Additional protective measures include implementing web filtering solutions that can detect and block suspicious HTML content, configuring network-level restrictions to prevent access to potentially malicious sites, and establishing monitoring systems to detect unusual application crash patterns that might indicate exploitation attempts. Organizations should also consider implementing alternative browsing solutions for critical systems or deploying sandboxing techniques to isolate vulnerable applications. The vulnerability highlights the importance of input validation and proper error handling in web browser implementations, serving as a reminder that even lightweight applications can contain critical security flaws that require regular security assessments and updates.