CVE-2016-2826 in Firefox
Summary
by MITRE
The maintenance service in Mozilla Firefox before 47.0 and Firefox ESR 45.x before 45.2 on Windows does not prevent MAR extracted-file modification during updater execution, which might allow local users to gain privileges via a Trojan horse file.
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Analysis
by VulDB Data Team • 10/23/2024
The vulnerability identified as CVE-2016-2826 represents a critical privilege escalation flaw in Mozilla Firefox's update mechanism on Windows operating systems. This issue affects Firefox versions prior to 47.0 and Firefox ESR 45.x versions prior to 45.2, specifically targeting the maintenance service responsible for handling software updates. The vulnerability stems from insufficient file integrity validation during the update process, creating a window of opportunity for malicious actors to exploit the system's trust model.
The technical flaw manifests in the maintenance service's failure to properly validate or protect extracted files during the updater execution phase. When Firefox performs automatic updates on Windows systems, it employs a maintenance service that extracts and processes various files to complete the update process. The vulnerability allows local attackers to substitute legitimate update files with malicious Trojan horse files that exploit this window of opportunity. This occurs because the system does not adequately verify file integrity or prevent modification of extracted files during the update process, which is categorized under CWE-276 as improper file permissions or inadequate access control.
The operational impact of this vulnerability is significant as it enables local privilege escalation attacks that can potentially allow attackers to execute arbitrary code with elevated privileges. An attacker who can place a malicious file in the update directory or manipulate the update process can effectively bypass the security model that Firefox employs to ensure only legitimate updates are installed. This creates a persistent threat vector where the malicious code can be executed during the update process, potentially compromising the entire system. The vulnerability aligns with ATT&CK technique T1068 which describes local privilege escalation through exploitation of system-level processes and services.
The attack vector for this vulnerability requires local system access, making it particularly dangerous in environments where users may have limited administrative privileges but can still influence the update process. Attackers typically exploit this by placing malicious files in locations where Firefox's maintenance service will attempt to extract or modify files during updates, often leveraging the trust model that the system places in the update mechanism itself. The exploitation process involves creating a Trojan horse file that mimics legitimate update components, allowing the malicious code to execute with the privileges of the maintenance service, which typically runs with elevated permissions.
Mitigation strategies for CVE-2016-2826 primarily focus on immediate software updates to patched versions of Firefox and Firefox ESR. Organizations should prioritize deploying Firefox 47.0 or later versions, or Firefox ESR 45.2 and later, which contain fixes that address the file modification vulnerability during the update process. Additional protective measures include implementing strict file permission controls on Firefox installation directories and update-related folders, monitoring for unauthorized file modifications in update directories, and employing endpoint protection solutions that can detect suspicious file replacement activities. System administrators should also consider implementing application whitelisting policies to restrict execution of unauthorized binaries during update processes, as recommended by cybersecurity frameworks such as NIST SP 800-171 for protecting sensitive information systems.