CVE-2014-1520 in Firefox
Summary
by MITRE
maintenservice_installer.exe in the Maintenance Service Installer in Mozilla Firefox before 29.0 and Firefox ESR 24.x before 24.5 on Windows allows local users to gain privileges by placing a Trojan horse DLL file into a temporary directory at an unspecified point in the update process.
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Analysis
by VulDB Data Team • 11/25/2025
The vulnerability identified as CVE-2014-1520 represents a privilege escalation flaw within Mozilla Firefox's Maintenance Service Installer component on Windows systems. This issue affects Firefox versions prior to 29.0 and Firefox ESR 24.x versions before 24.5, creating a significant security risk for Windows users who may be exploited through malicious DLL insertion techniques. The vulnerability specifically targets the installer executable named maintenservice_installer.exe which handles the maintenance service installation process for Firefox updates.
The technical flaw stems from improper handling of temporary directories during the Firefox update process where the installer does not adequately verify the integrity of DLL files loaded from temporary locations. Attackers can exploit this weakness by placing a malicious Trojan horse DLL file in a temporary directory, which the installer will subsequently load and execute with elevated privileges. This occurs because the installer does not implement proper DLL search order security measures or digital signature verification for dynamically loaded components. The vulnerability operates under the principle of DLL hijacking where legitimate system processes load malicious code from predictable temporary locations without proper validation.
The operational impact of this vulnerability is substantial as it allows local attackers to escalate their privileges from standard user level to system level execution. Once successful, the malicious DLL gains the same privileges as the Firefox maintenance service, potentially enabling full system compromise, data exfiltration, or persistence mechanisms. The attack vector is particularly concerning because it leverages the legitimate update process of a widely used browser, making it difficult to detect and preventing users from recognizing the compromise. This type of attack aligns with the attack technique described in the MITRE ATT&CK framework under privilege escalation through DLL hijacking and component injection.
The vulnerability also relates to CWE-427 Uncontrolled Search Path Element, which describes how applications that search for files in a list of directories without proper validation or sanitization can be exploited. Additionally, it connects to CWE-426 Untrusted Search Path, where applications fail to properly validate the source of dynamically loaded libraries. Organizations running affected Firefox versions face significant risk, as this vulnerability can be exploited by attackers with minimal privileges to achieve system compromise. The risk is amplified because the update process is designed to run with elevated privileges, creating an ideal attack window for privilege escalation.
Effective mitigations for this vulnerability include immediate patching of affected Firefox versions to 29.0 or later for regular releases, and 24.5 or later for ESR versions. System administrators should also implement proper file system permissions on temporary directories, disable unnecessary auto-update functionality, and monitor for unauthorized DLL file placements in system directories. Additional defensive measures include deploying application whitelisting solutions that restrict which DLLs can be loaded by the Firefox maintenance service installer, implementing proper DLL search order policies, and conducting regular security audits of temporary file directories. Organizations should also consider network-based monitoring to detect suspicious file placement activities in temporary directories during update processes, which aligns with security best practices outlined in the NIST Cybersecurity Framework for protecting against privilege escalation attacks.