CVE-2026-74950 in Firefox
Summary
by MITRE • 08/18/2026
Privilege escalation in the Downloads API component. This vulnerability was fixed in Firefox 154 and Firefox ESR 153.1.
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Analysis
by VulDB Data Team • 08/18/2026
The identified security issue represents a critical privilege escalation flaw located within the Downloads API component of Mozilla Firefox, specifically affecting versions prior to 154 and Firefox Extended Support Release (ESR) version 153.1. This vulnerability stems from an improper handling of access controls or state management during file download operations, allowing a lower-privileged context, such as content running in a web page, to manipulate the browser's internal processes with elevated permissions. In modern browsers like Firefox, the Downloads API is designed to manage user-initiated and programmatic downloads while maintaining strict sandboxing boundaries between untrusted web content and privileged browser components. When this boundary is compromised due to logic errors or insufficient validation of input parameters within the download manager interface, an attacker can exploit the discrepancy to execute actions that should be restricted to higher-privilege contexts.
From a technical perspective, privilege escalation vulnerabilities in browser APIs often arise when internal methods fail to verify whether the caller has the necessary permissions before performing sensitive operations such as writing files to arbitrary locations, modifying system settings, or accessing protected resources. In this specific case, the flaw likely involves the Downloads API accepting inputs from untrusted sources without adequate sanitization or permission checks, thereby enabling a malicious web page to trigger download-related functions that bypass intended security restrictions. This could allow an attacker to write files outside of designated directories, potentially overwriting system-critical files if they can predict file paths, or manipulating browser state in ways that facilitate further exploitation chains such as cross-site scripting persistence or data exfiltration through disguised downloads.
The operational impact of this vulnerability is severe because it undermines the fundamental security model of the web platform by breaking isolation between tabs and extensions. An attacker who successfully exploits this flaw could gain unauthorized access to sensitive user data, install malicious software without explicit user consent under certain configurations, or use the browser as a pivot point for further network attacks. Since downloads are often perceived by users as benign actions, they serve as a common vector for initial compromise; therefore, elevating privileges through the download mechanism significantly increases the success rate and impact of drive-by exploitation attempts. Users running affected versions remain exposed to risks including data theft, system integrity violation, and potential remote code execution if combined with other vulnerabilities in file handling subsystems.
To mitigate this risk, organizations and individual users must ensure that Firefox is updated immediately to version 154 or later for standard releases, or version 153.1 for ESR channels. These updates contain the necessary patches that enforce stricter permission checks within the Downloads API and correct the logic errors responsible for the privilege escalation. Additionally, administrators should implement application whitelisting policies where feasible to restrict unauthorized file modifications even if a browser vulnerability is exploited. Monitoring download activity through endpoint detection and response solutions can also help identify anomalous behavior indicative of exploitation attempts. Regular patch management cycles are essential to maintain defense-in-depth strategies against such high-severity vulnerabilities that target core browser functionalities.