CVE-2026-74965 in Firefox
Summary
by MITRE • 08/18/2026
Privilege escalation in the Shell Integration component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, and Firefox ESR 153.1.
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Analysis
by VulDB Data Team • 08/19/2026
The identified vulnerability represents a critical privilege escalation flaw located within the shell integration subsystem of Mozilla Firefox browsers. Shell integration components are responsible for managing interactions between the browser application and the underlying operating system's file handlers, default applications, and context menus. These interfaces require elevated permissions to function correctly, as they must be able to launch external processes or modify user interface elements that affect system-wide behavior. When this subsystem contains a logic error or improper access control check, it creates an avenue for attackers to bypass standard security boundaries. The vulnerability allows a malicious actor who has already achieved code execution within the browser's sandboxed environment to escalate their privileges to those of the currently logged-in user. This escalation is significant because it effectively breaks out of the restrictive container that protects the rest of the system from compromised web content, granting the attacker broader access to local files, settings, and potentially other applications running on the host machine.
From a technical perspective, this type of flaw typically stems from improper validation of input parameters passed between the browser's internal components and the operating system APIs. In many cases, shell integration vulnerabilities arise when the application fails to sanitize commands or file paths before executing them through system shells or registry keys. An attacker could exploit this by crafting a malicious webpage that triggers specific JavaScript calls designed to invoke these privileged functions with unexpected arguments. By manipulating how the browser interprets and executes these requests, the adversary can trick the shell integration module into performing actions it was not intended to allow under normal circumstances. This might include writing files to protected directories, modifying registry entries that control application behavior, or executing arbitrary binaries with user-level privileges. The core issue lies in the assumption that content originating from web pages is untrusted while simultaneously granting those same sources access to high-privilege system interfaces without sufficient verification of intent and context.
The operational impact of this vulnerability is severe due to its potential for lateral movement and data exfiltration within a compromised endpoint. Once an attacker achieves user-level privileges through shell integration exploitation, they are no longer confined by the browser's sandbox restrictions. This means that sensitive documents stored in standard user directories become accessible, allowing for targeted theft of intellectual property or personal identifiable information. Furthermore, with elevated access, the adversary can install persistent malware such as keyloggers, remote access trojans, or credential harvesters that operate under the guise of legitimate system processes. The ability to modify application associations and default handlers also enables phishing attacks where clicking a link in an email might inadvertently launch a malicious executable rather than opening it safely in the browser. This significantly expands the attack surface beyond simple data theft into full system compromise, facilitating long-term unauthorized access and deeper infiltration within corporate networks if the affected machine is part of a larger infrastructure.
Mitigation strategies for this vulnerability rely primarily on prompt software updates to ensure that all instances of Firefox are running versions where the flaw has been patched. Users should immediately upgrade to Firefox version 154 or later, as well as any supported Extended Support Release (ESR) branches including ESR 140.14 and ESR 153.1. These updates contain code changes that enforce stricter validation on shell integration calls and restrict the permissions granted to web content when interacting with system-level features. In addition to updating software, organizations should implement application whitelisting policies to prevent unauthorized executables from running even if an attacker gains user privileges. Network segmentation can also help limit the spread of malware once a single endpoint is compromised by restricting communication between internal systems and external command-and-control servers. Security awareness training remains essential as well, since many initial compromises begin with social engineering tactics that trick users into visiting malicious sites or downloading infected files in the first place.
This vulnerability aligns closely with Common Weakness Enumeration (CWE) categories related to improper privilege management and insecure interaction between components. Specifically it reflects weaknesses associated with CWE-269 which covers Improper Privilege Management, where a process does not properly enforce its own security policy or access control lists. It also relates to CWE-78 involving OS Command Injection if the shell integration flaw allows for arbitrary command execution through unsanitized inputs passed to system shells. From an offensive security perspective this behavior maps directly to MITRE ATT&CK technique T1059 which describes Command and Scripting Interpreter usage, particularly when used by malware or attackers to execute commands on a compromised host. Understanding these mappings helps defenders prioritize remediation efforts based on established industry frameworks that categorize risks according to their likelihood of exploitation and potential impact on confidentiality integrity and availability.