CVE-2017-7760 in Firefox
Summary
by MITRE
The Mozilla Windows updater modifies some files to be updated by reading the original file and applying changes to it. The location of the original file can be altered by a malicious user by passing a special path to the callback parameter through the Mozilla Maintenance Service, allowing the manipulation of files in the installation directory and privilege escalation by manipulating the Mozilla 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 identified as CVE-2017-7760 represents a critical privilege escalation flaw within Mozilla Firefox's Windows updater mechanism. This weakness stems from the improper handling of file paths during the update process, specifically within the Mozilla Maintenance Service component that operates with elevated privileges. The vulnerability manifests when the updater reads original files and applies modifications, but fails to properly validate or sanitize the paths provided through the callback parameter. This design flaw creates an attack vector where malicious actors can manipulate file locations by crafting specific paths that redirect the updater to target files outside the intended installation directory. The security implications are particularly severe because the Mozilla Maintenance Service operates with system-level privileges, making any path manipulation potentially catastrophic for system integrity. The vulnerability affects Firefox Extended Support Release versions prior to 52.2 and standard Firefox versions prior to 54, representing a significant portion of the user base at the time of discovery. This issue falls under the CWE-22 category of Improper Limitation of a Pathname to a Restricted Directory, commonly known as Path Traversal, which is a well-documented weakness in software security. The ATT&CK framework categorizes this vulnerability under privilege escalation techniques, specifically leveraging service execution and file system permissions to gain elevated access.
The technical exploitation of this vulnerability requires local system access, meaning an attacker must already have user-level access to the target system to initiate the attack. However, the impact is severe because once the malicious path is passed through the callback parameter to the Mozilla Maintenance Service, the updater will execute with the privileges of the service account, typically SYSTEM level access. This allows attackers to manipulate critical system files, modify executable components, or inject malicious code into the Firefox installation directory. The updater's process of reading original files and applying changes creates a window where an attacker can control what files are being modified, potentially replacing legitimate executables with malicious payloads. The vulnerability is specifically Windows-only due to the implementation details of the Mozilla Maintenance Service and Windows file system permissions, making it irrelevant to other operating systems like Linux or macOS. The attack chain involves crafting a malicious path that bypasses normal file system restrictions, leveraging the service's elevated privileges to write or modify files in locations where normal user accounts would not have access. This creates a sophisticated attack scenario where the initial compromise occurs through local access, but the exploitation results in system-level control.
The operational impact of CVE-2017-7760 extends beyond simple privilege escalation to potentially enable full system compromise when combined with other attack vectors. An attacker who successfully exploits this vulnerability can effectively take control of the target system, as the Mozilla Maintenance Service operates with sufficient privileges to modify core system components. This vulnerability represents a significant risk to enterprise environments where Firefox is widely deployed, as it could allow attackers to establish persistent access or deploy additional malware. The update mechanism becomes a trusted entry point for malicious code execution, as legitimate update processes are leveraged for unauthorized file modifications. Organizations using older versions of Firefox ESR or standard Firefox before the patched versions are particularly vulnerable, as these releases contain the exploitable code path. The attack requires minimal sophistication beyond understanding how to manipulate the callback parameter, making it accessible to attackers with basic knowledge of the Firefox update architecture. Security teams must consider this vulnerability as part of their overall risk assessment for Firefox deployments, particularly in environments where local access control is insufficient. The vulnerability demonstrates the importance of secure coding practices in update mechanisms, as the same pattern of reading and modifying files can be exploited if proper path validation is not implemented. The combination of the Mozilla Maintenance Service's privileged access with the lack of input sanitization creates a dangerous scenario where file system manipulation becomes a weapon for system compromise.
Mitigation strategies for CVE-2017-7760 focus on both immediate remediation and long-term architectural improvements. The primary and most effective solution is to upgrade to Firefox ESR 52.2 or Firefox 54 and later versions, which contain patches that properly validate file paths and prevent malicious path manipulation. Organizations should implement strict access controls to prevent unauthorized local access to systems running vulnerable Firefox versions, as this vulnerability cannot be exploited remotely. Security administrators should monitor for suspicious file modifications in Firefox installation directories, particularly around executable files and service components. The Mozilla Maintenance Service should be configured with minimal required privileges, though this may not be possible due to the service's legitimate operational requirements. Network segmentation and endpoint protection solutions can help detect unusual patterns of file system access that might indicate exploitation attempts. Regular security audits of update mechanisms and service configurations should be conducted to identify similar vulnerabilities in other software components. The vulnerability highlights the importance of implementing proper input validation and path sanitization in all file operations, particularly those involving privileged services. Organizations should also consider implementing application whitelisting policies to prevent unauthorized executable modifications. The ATT&CK framework suggests monitoring for service execution and file system modifications as part of defensive strategies against this class of vulnerabilities. Additionally, security awareness training for system administrators should emphasize the risks associated with local privilege escalation and the importance of keeping software updated. Organizations should maintain comprehensive backup strategies to quickly restore systems compromised by this vulnerability, as the exploitation could result in complete system compromise. The vulnerability serves as a reminder of the critical importance of secure update mechanisms and the potential consequences when privilege separation is not properly implemented in software components.