CVE-2016-9179 in Lynx
Summary
by MITRE
lynx: It was found that Lynx doesn't parse the authority component of the URL correctly when the host name part ends with '?', and could instead be tricked into connecting to a different host.
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Analysis
by VulDB Data Team • 09/17/2024
The vulnerability identified as CVE-2016-9179 affects the Lynx web browser, a widely used text-based web client that operates in terminal environments. This issue stems from a critical flaw in how Lynx processes Uniform Resource Locator (URL) components, specifically the authority section that contains host information. The vulnerability manifests when a URL contains a host name that terminates with a question mark character, creating a parsing anomaly that can lead to significant security implications.
The technical flaw resides in Lynx's URL parsing algorithm which fails to correctly handle the authority component when the hostname portion concludes with a question mark. This parsing error occurs because the browser does not properly distinguish between the host identifier and the query parameters within the URL structure. When encountering such malformed URLs, the browser incorrectly interprets the portion of the URL following the question mark as part of the host specification rather than as query data, potentially causing the application to establish connections to unintended hosts.
This vulnerability creates a substantial operational impact by enabling malicious actors to craft deceptive URLs that could redirect Lynx users to unauthorized destinations. The flaw essentially allows for host name manipulation through URL construction, potentially facilitating man-in-the-middle attacks, phishing attempts, or unauthorized network connections. When users navigate to specifically crafted URLs ending with question marks, they may inadvertently connect to different hosts than those specified in the original URL, bypassing normal security checks and potentially exposing sensitive information.
The vulnerability aligns with CWE-1009, which addresses improper handling of malformed input during URL parsing operations, and demonstrates characteristics consistent with CWE-347, concerning improper validation of certificates and authentication. From an ATT&CK framework perspective, this issue maps to T1071.004 for application layer protocol: DNS and T1566 for credential access through social engineering, as the vulnerability enables attackers to manipulate user navigation and potentially harvest credentials. Organizations relying on Lynx for web browsing, particularly in environments where security is paramount, face increased risk of unauthorized access and data interception. The flaw particularly affects systems where Lynx is used for automated processes or where users may encounter untrusted web content, as the vulnerability can be exploited without requiring user interaction beyond visiting the malicious URL.
Mitigation strategies should include immediate patching of Lynx installations to address the URL parsing flaw, implementation of network-level controls to filter suspicious URL patterns, and user education regarding the dangers of visiting untrusted web content. System administrators should also consider deploying URL filtering solutions that can detect and block URLs containing malformed host specifications ending with question marks. Additionally, organizations should conduct regular security assessments to identify other potential parsing vulnerabilities in similar text-based browsers and web clients that may exhibit similar behaviors. The vulnerability serves as a reminder of the critical importance of robust input validation in network applications, particularly those operating in security-sensitive environments where text-based interfaces are prevalent.