CVE-2009-4102 in Sage
Summary
by MITRE
Sage 1.4.3 and earlier extension for Firefox performs certain operations with chrome privileges, which allows remote attackers to execute arbitrary commands and perform cross-domain scripting attacks via the description tag of an RSS feed.
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Analysis
by VulDB Data Team • 02/10/2025
The vulnerability identified as CVE-2009-4102 represents a critical security flaw in the Sage extension for Firefox versions 1.4.3 and earlier. This extension, designed to enhance browser functionality, contains a dangerous privilege escalation mechanism that enables remote attackers to execute arbitrary code on affected systems. The vulnerability specifically manifests through the improper handling of the description tag within RSS feed content, creating a vector for sophisticated attacks that bypass standard browser security boundaries.
The technical flaw stems from the extension's improper implementation of chrome privileges, which are typically restricted to trusted browser components and extensions. When Firefox processes RSS feeds containing specially crafted description tags, the Sage extension inadvertently elevates its privileges to chrome-level access, allowing malicious actors to execute arbitrary commands on the target system. This privilege escalation occurs because the extension fails to properly validate or sanitize input from external RSS sources, creating a direct pathway for code execution. The vulnerability operates at the intersection of improper input validation and privilege management, which aligns with CWE-20 (Improper Input Validation) and CWE-264 (Permissions, Privileges, and Access Controls) categories.
The operational impact of this vulnerability extends beyond simple command execution to encompass comprehensive system compromise and cross-domain scripting capabilities. Attackers can leverage this flaw to perform actions such as file system access, registry modification, network communication, and data exfiltration from the victim's machine. The cross-domain scripting aspect enables attackers to bypass standard web security restrictions and access resources across different domains, potentially leading to session hijacking, data theft, or further exploitation of the compromised system. This vulnerability represents a significant threat to users who regularly consume RSS feeds, as the attack can be initiated through seemingly benign content from trusted sources.
The attack surface for this vulnerability is particularly concerning given the widespread use of RSS feeds and the prevalence of the Sage extension in Firefox environments. The exploit requires minimal user interaction beyond viewing an infected RSS feed, making it highly effective for mass deployment. Security researchers have documented similar patterns in other browser extension vulnerabilities where insufficient privilege boundaries and input sanitization flaws create persistent attack vectors. Organizations should consider this vulnerability in their threat modeling and incident response planning, particularly when assessing risks associated with browser extensions and third-party content processing.
Mitigation strategies for CVE-2009-4102 focus on immediate remediation through extension updates and browser security hardening. Users should upgrade to Sage extension versions that address the privilege escalation flaw and implement proper input validation for RSS feed content. Organizations should consider disabling the Sage extension in enterprise environments until proper updates are deployed and implement network monitoring to detect suspicious RSS feed activity. The vulnerability demonstrates the critical importance of privilege separation in browser extensions and highlights the need for robust input validation mechanisms. Security teams should also consider implementing content security policies and restricting browser extension permissions to minimize the impact of similar vulnerabilities in the future. This case study reinforces the ATT&CK framework principle that privilege escalation and code execution through browser extensions represents a common attack pattern that requires comprehensive defensive measures.