CVE-2024-32463 in phlex
Summary
by MITRE • 04/17/2024
phlex is an open source framework for building object-oriented views in Ruby. There is a potential cross-site scripting (XSS) vulnerability that can be exploited via maliciously crafted user data. The filter to detect and prevent the use of the `javascript:` URL scheme in the `href` attribute of an `` tag could be bypassed with tab `\t` or newline `\n` characters between the characters of the protocol, e.g. `java\tscript:`. This vulnerability is fixed in 1.10.1, 1.9.2, 1.8.3, 1.7.2, 1.6.3, 1.5.3, and 1.4.2. Configuring a Content Security Policy that does not allow `unsafe-inline` would effectively prevent this vulnerability from being exploited.
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Analysis
by VulDB Data Team • 04/05/2025
The CVE-2024-32463 vulnerability affects phlex, an open source ruby framework designed for building object-oriented views. This framework provides developers with tools to construct web interfaces using ruby syntax, making it a critical component in ruby web application development. The vulnerability stems from insufficient input validation mechanisms within the framework's html sanitization process, specifically concerning the handling of javascript protocol URLs in hyperlink attributes. Security researchers identified that the framework's existing protection measures against malicious javascript: URLs were inadequate, creating a pathway for attackers to bypass security controls through carefully crafted input manipulation techniques.
The technical flaw manifests in the framework's URL protocol validation logic where it fails to properly sanitize whitespace characters that can be inserted between protocol characters. Attackers can exploit this by inserting tab characters or newline sequences between the letters of javascript:, creating a bypassed variant such as java script: that evades the existing filter mechanisms. This type of vulnerability falls under CWE-79 - Cross-site Scripting and specifically demonstrates weaknesses in input validation and output encoding. The vulnerability occurs at the application layer where user-supplied data is processed and rendered into html content without proper sanitization of potentially malicious protocol specifications. The bypass mechanism relies on the fact that web browsers interpret tab and newline characters as whitespace that can separate protocol identifiers, effectively circumventing simple string matching approaches used in the original sanitization logic.
The operational impact of this vulnerability is significant for applications utilizing the phlex framework, as it allows attackers to inject malicious javascript code into web pages through user input fields. This creates opportunities for session hijacking, credential theft, and arbitrary code execution within the context of affected web applications. The vulnerability affects multiple versions of the framework, indicating a widespread exposure across different release lines and potentially impacting numerous production systems. Organizations using phlex for web application development face increased risk of client-side attacks, particularly in applications that accept untrusted user input and render it directly into html content. The exploitation requires minimal technical skill and can be automated, making it particularly dangerous in environments where user input is not properly validated or sanitized.
Mitigation strategies for this vulnerability include immediate upgrade to patched versions 1.10.1, 1.9.2, 1.8.3, 1.7.2, 1.6.3, 1.5.3, and 1.4.2, which contain proper sanitization logic that handles whitespace characters in protocol specifications. Additionally, implementing a robust Content Security Policy (CSP) that explicitly blocks unsafe-inline scripts provides an effective defense-in-depth measure that can prevent exploitation even if the underlying framework vulnerability persists. Security teams should also conduct thorough code reviews to identify other potential bypass opportunities in similar input validation mechanisms and implement comprehensive testing procedures for user input sanitization. The vulnerability demonstrates the importance of considering all possible character combinations and whitespace sequences when implementing security filters, aligning with ATT&CK technique T1203 - Exploitation for Client Execution which emphasizes the need for proper input validation to prevent client-side exploitation. Organizations should also consider implementing web application firewalls and runtime application self-protection mechanisms to provide additional layers of defense against similar input-based vulnerabilities.