CVE-2017-7766 in Firefox
Summary
by MITRE
An attack using manipulation of "updater.ini" contents, used by the Mozilla Windows Updater, and privilege escalation through the Mozilla Maintenance Service to allow for arbitrary file execution and deletion by the Maintenance Service, which has privileged access. Note: This attack requires local system access and only affects Windows. Other operating systems are not affected. This vulnerability affects Firefox ESR < 52.2 and Firefox < 54.
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Analysis
by VulDB Data Team • 11/26/2025
The vulnerability described in CVE-2017-7766 represents a sophisticated privilege escalation attack targeting the Mozilla Windows Updater component and the Mozilla Maintenance Service on Windows operating systems. This flaw demonstrates how seemingly benign configuration files can be exploited to gain elevated system privileges, creating a critical security risk for affected Firefox versions. The attack vector specifically leverages manipulation of the updater.ini file, which serves as a configuration mechanism for the Windows updater process. The vulnerability is particularly concerning because it requires only local system access to exploit, meaning an attacker with basic user privileges can potentially elevate their access level to system level through this mechanism.
The technical implementation of this vulnerability involves the manipulation of the updater.ini configuration file that is processed by the Mozilla Windows Updater component. When the Mozilla Maintenance Service executes, it reads this configuration file and processes its contents with elevated privileges. This creates a dangerous scenario where an attacker can inject malicious content into the updater.ini file, which then gets executed with system-level privileges by the Maintenance Service. The flaw essentially creates a path for arbitrary file execution and deletion operations through the privileged maintenance service, bypassing normal access controls and system protections. This represents a classic privilege escalation vulnerability where a service running with elevated privileges is tricked into executing attacker-controlled code through a manipulated configuration file.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass potential full system compromise. Attackers who successfully exploit this vulnerability can execute arbitrary code with system-level privileges, potentially leading to complete system takeover. The maintenance service has broad access to system resources and can perform operations such as installing malicious software, modifying system files, or creating persistent backdoors. The affected software versions include Firefox ESR versions prior to 52.2 and Firefox versions prior to 54, indicating that this vulnerability existed for several release cycles and affected a significant portion of the Firefox user base. This vulnerability is particularly dangerous because it operates silently in the background and can be exploited without user interaction beyond gaining local system access.
Mitigation strategies for CVE-2017-7766 focus primarily on updating to patched versions of Firefox and implementing proper file access controls. The most effective immediate solution is upgrading to Firefox ESR 52.2 or later versions, or Firefox 54 and later, which contain patches that address the privilege escalation mechanism. Organizations should also implement strict file permissions on the updater.ini file and related maintenance service components to prevent unauthorized modification. The vulnerability aligns with CWE-276, which covers improper file permissions, and demonstrates how insecure file handling can lead to privilege escalation. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques using service misconfiguration and file manipulation, specifically targeting the maintenance service component that operates with elevated privileges. System administrators should also consider implementing monitoring solutions to detect unauthorized modifications to critical configuration files and maintain regular patching schedules to prevent exploitation of similar vulnerabilities in the future.