CVE-2016-9422 in w3m
Summary
by MITRE
An issue was discovered in the Tatsuya Kinoshita w3m fork before 0.5.3-31. The feed_table_tag function in w3m doesn't properly validate the value of table span, which allows remote attackers to cause a denial of service (stack and/or heap buffer overflow) and possibly execute arbitrary code via a crafted HTML page.
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Analysis
by VulDB Data Team • 06/25/2019
The vulnerability identified as CVE-2016-9422 affects the w3m web browser fork developed by Tatsuya Kinoshita and represents a critical security flaw in the feed_table_tag function implementation. This issue exists in versions prior to 0.5.3-31 and demonstrates a classic buffer overflow vulnerability that can be exploited through maliciously crafted HTML content. The flaw specifically targets the table span value validation mechanism, which fails to properly sanitize or limit input parameters during HTML parsing operations.
The technical implementation of this vulnerability stems from inadequate bounds checking within the feed_table_tag function where table span attributes are processed without proper validation of their numerical values. When a remote attacker crafts an HTML page containing malicious table span values, the w3m browser fails to enforce reasonable limits on these parameters, leading to memory corruption conditions. This memory corruption can manifest as either stack-based or heap-based buffer overflow conditions depending on the specific execution context and input parameters provided by the attacker.
From an operational impact perspective, this vulnerability creates significant security risks for users of the affected w3m versions. The potential for remote code execution represents a severe threat vector that could allow attackers to gain unauthorized control over affected systems. Additionally, the denial of service component means that simply visiting a malicious webpage could crash the browser application, disrupting normal user operations and potentially enabling more sophisticated attack scenarios. The vulnerability's exploitation requires only web-based delivery mechanisms, making it particularly dangerous in environments where users frequently browse untrusted content.
The attack surface for this vulnerability aligns with CWE-121, which categorizes buffer overflow conditions in stack-based memory allocation, and CWE-122, which covers heap-based buffer overflows. These classifications indicate that the flaw involves improper handling of memory boundaries during dynamic allocation operations. The vulnerability also maps to ATT&CK technique T1059.007, which covers command and scripting interpreter usage through web-based attacks, as attackers could potentially leverage this flaw to execute arbitrary commands on compromised systems.
Mitigation strategies for CVE-2016-9422 primarily involve upgrading to w3m version 0.5.3-31 or later, which contains the necessary patches to address the table span validation issue. System administrators should also implement network-based security controls such as web application firewalls that can detect and block malicious HTML content containing suspicious table span parameters. Additional protective measures include disabling automatic HTML rendering in web browsers, implementing strict content filtering policies, and conducting regular security assessments to identify potentially vulnerable systems. Users should be educated about the risks of visiting untrusted websites and the importance of keeping their browser software updated to prevent exploitation of known vulnerabilities.