CVE-2012-4210 in Firefox
Summary
by MITRE
The Style Inspector in Mozilla Firefox before 17.0 and Firefox ESR 10.x before 10.0.11 does not properly restrict the context of HTML markup and Cascading Style Sheets (CSS) token sequences, which allows user-assisted remote attackers to execute arbitrary JavaScript code with chrome privileges via a crafted stylesheet.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 10/22/2024
The vulnerability identified as CVE-2012-4210 represents a critical security flaw in Mozilla Firefox's Style Inspector component that existed across multiple versions including Firefox 16.0 and earlier, as well as Firefox ESR 10.x versions prior to 10.0.11. This issue stems from inadequate validation mechanisms within the browser's stylesheet processing capabilities, specifically affecting how the Style Inspector handles HTML markup and CSS token sequences. The flaw operates as a privilege escalation vulnerability that enables attackers to execute malicious JavaScript code with chrome privileges, which represents a significant security risk given the elevated permissions typically associated with browser chrome contexts.
The technical root cause of this vulnerability lies in the improper restriction of context within Firefox's Style Inspector functionality. When processing crafted stylesheets, the browser fails to adequately sanitize or validate the input sequences, allowing malicious code to be interpreted and executed within the privileged chrome environment. This occurs because the Style Inspector does not properly isolate or validate CSS token sequences that contain embedded HTML markup, creating a pathway for attackers to inject and execute arbitrary JavaScript code. The vulnerability specifically affects how Firefox processes stylesheet data, particularly when the browser's internal rendering engine encounters malformed or specially crafted CSS that includes embedded markup elements.
The operational impact of CVE-2012-4210 is severe and far-reaching, as it allows remote attackers to execute arbitrary code with elevated privileges within the browser environment. Attackers can leverage this vulnerability through user-assisted means by crafting malicious stylesheets that, when loaded or processed by the vulnerable Firefox versions, trigger the execution of malicious JavaScript code with chrome privileges. This capability enables attackers to perform actions such as accessing sensitive user data, modifying browser behavior, executing arbitrary commands on the underlying system, and potentially escalating their attack to compromise the entire user environment. The vulnerability essentially allows attackers to bypass normal browser security boundaries and gain access to privileged execution contexts that should remain restricted to browser internals.
This vulnerability aligns with CWE-20, which describes improper input validation, and represents a classic example of a code injection vulnerability that operates within the context of web browser security. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and code injection within browser environments, specifically targeting the browser's rendering and styling engines. The attack vector requires user interaction to load or process a malicious stylesheet, making it a user-assisted remote code execution vulnerability that demonstrates the critical importance of proper input sanitization and context validation in browser security implementations. Organizations and users were strongly advised to upgrade to patched versions of Firefox to mitigate this vulnerability, as the flaw could be exploited without requiring any special privileges from the attacker beyond the ability to deliver a malicious stylesheet to a victim's browser.
The remediation for CVE-2012-4210 required Mozilla to implement proper input validation and context restriction within the Style Inspector component, ensuring that CSS token sequences are properly sanitized and that HTML markup embedded within stylesheets is appropriately handled without compromising security boundaries. This fix involved strengthening the validation mechanisms that govern how Firefox processes and interprets stylesheet data, particularly focusing on preventing the execution of embedded JavaScript code within privileged contexts. The patched versions of Firefox addressed the core issue by implementing more robust sanitization routines and ensuring that the Style Inspector maintains proper isolation between user-provided content and the browser's privileged execution environments, thereby preventing the exploitation of this vulnerability through crafted stylesheet inputs.