CVE-2009-5065 in Universal Feed Parser
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in feedparser.py in Universal Feed Parser (aka feedparser or python-feedparser) before 5.0 allows remote attackers to inject arbitrary web script or HTML via vectors involving nested CDATA stanzas.
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Analysis
by VulDB Data Team • 01/13/2025
The vulnerability identified as CVE-2009-5065 represents a critical cross-site scripting flaw within the Universal Feed Parser library, specifically in the feedparser.py module. This library serves as a fundamental component for parsing rss and atom feeds across numerous web applications and systems, making its security implications particularly severe. The vulnerability exists in versions prior to 5.0 of the Universal Feed Parser, which is a widely adopted python library for processing syndication feeds. The flaw manifests when the parser encounters nested CDATA stanzas within feed content, creating an avenue for malicious actors to execute arbitrary web scripts or HTML code within the context of affected applications.
The technical mechanism behind this vulnerability stems from inadequate input sanitization within the feed parsing process. When the feedparser encounters nested CDATA sections, the parser fails to properly escape or validate the content contained within these structures, allowing attacker-controlled data to bypass normal security measures. This occurs because the parser does not adequately distinguish between legitimate feed content and malicious script code, particularly when dealing with complex nested structures that may contain multiple CDATA sections. The vulnerability specifically exploits the way the parser handles these nested elements, which can contain embedded HTML or script tags that are subsequently rendered in web browsers without proper sanitization.
The operational impact of this vulnerability extends far beyond simple script execution, as it enables attackers to perform a wide range of malicious activities within the context of affected applications. An attacker could inject malicious javascript code that steals user session cookies, redirects users to phishing sites, or modifies the content displayed to unsuspecting users. This vulnerability is particularly dangerous because it can be exploited through feed aggregation systems, content management platforms, and any application that relies on Universal Feed Parser to display feed content. The attack vector requires no special privileges or complex exploitation techniques, making it accessible to attackers of varying skill levels and potentially affecting thousands of applications that depend on this library.
Mitigation strategies for CVE-2009-5065 primarily involve upgrading to Universal Feed Parser version 5.0 or later, where the vulnerability has been addressed through improved input validation and sanitization mechanisms. Organizations should conduct comprehensive inventory assessments to identify all systems utilizing vulnerable versions of the library and prioritize remediation efforts accordingly. Additionally, implementing proper content filtering at the application level, such as using HTML sanitization libraries, can provide additional protection layers. The vulnerability aligns with CWE-79, which categorizes cross-site scripting flaws, and represents a classic example of how insecure input handling can lead to severe client-side exploitation. From an ATT&CK perspective, this vulnerability maps to techniques involving code injection and session hijacking, demonstrating how feed parsing vulnerabilities can serve as entry points for broader compromise of web applications and user data.
The broader implications of this vulnerability highlight the critical importance of secure input processing in library components that handle untrusted data from external sources. Given that feed parsers are fundamental building blocks in many web applications, vulnerabilities in these components can have cascading effects across entire ecosystems. Security practitioners should emphasize the need for regular library updates and maintain comprehensive vulnerability management processes that include monitoring for security advisories related to commonly used third-party components. The vulnerability also underscores the importance of defensive programming practices, particularly in applications that process external data feeds, where proper input validation and output encoding should be implemented as fundamental security controls.