CVE-2012-1957 in Firefox
Summary
by MITRE
An unspecified parser-utility class in Mozilla Firefox 4.x through 13.0, Firefox ESR 10.x before 10.0.6, Thunderbird 5.0 through 13.0, Thunderbird ESR 10.x before 10.0.6, and SeaMonkey before 2.11 does not properly handle EMBED elements within description elements in RSS feeds, which allows remote attackers to conduct cross-site scripting (XSS) attacks via a feed.
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Analysis
by VulDB Data Team • 10/21/2024
The vulnerability described in CVE-2012-1957 represents a critical cross-site scripting flaw affecting multiple Mozilla products including Firefox, Thunderbird, and SeaMonkey. This issue stems from improper handling of EMBED elements within RSS feed description elements, creating a pathway for remote attackers to execute malicious scripts in the context of a user's browser session. The vulnerability affects a broad range of versions including Firefox 4.x through 13.0, Firefox ESR 10.x before 10.0.6, Thunderbird 5.0 through 13.0, Thunderbird ESR 10.x before 10.0.6, and SeaMonkey before 2.11, indicating a widespread impact across the Mozilla ecosystem.
The technical flaw manifests in the parser-utility class responsible for processing RSS feed content, specifically when encountering EMBED elements nested within description elements. When a malicious RSS feed contains crafted EMBED tags with embedded JavaScript or other malicious content, the parser fails to properly sanitize or escape these elements before rendering them in the browser context. This improper handling allows attackers to inject arbitrary code that executes with the privileges of the victim's browser session, potentially leading to session hijacking, credential theft, or further exploitation of the victim's system. The vulnerability operates at the application layer and specifically targets the XML parsing and rendering components that process syndication feeds.
The operational impact of this vulnerability is significant as it enables attackers to leverage RSS feeds as a delivery mechanism for XSS attacks without requiring any user interaction beyond viewing the malicious feed. Attackers can craft malicious RSS feeds containing EMBED elements with script tags or other malicious content, which when consumed by vulnerable applications will execute automatically. This creates a vector for phishing attacks, credential harvesting, and potentially more sophisticated attacks that can leverage the victim's browser context to perform actions such as modifying browser settings, accessing local storage, or communicating with other services. The vulnerability is particularly dangerous because RSS feeds are commonly consumed by users through various applications and browsers, making the attack surface quite broad.
This vulnerability maps directly to CWE-79, which describes Cross-Site Scripting flaws in web applications, and aligns with ATT&CK technique T1212, which covers exploitation of software vulnerabilities to gain access to systems. The attack chain typically involves an attacker publishing a malicious RSS feed containing crafted EMBED elements, which are then consumed by vulnerable applications. The mitigation strategy involves updating to patched versions of the affected software, implementing proper input sanitization for RSS feed content, and potentially employing content security policies to prevent execution of unauthorized scripts. Organizations should prioritize patching affected systems and consider implementing feed filtering mechanisms to prevent potentially malicious content from reaching end users. The vulnerability demonstrates the importance of proper input validation and sanitization in parser components that handle external data feeds, as these components often serve as attack vectors for more sophisticated exploitation techniques.