CVE-2026-109770 in Firefox
Summary
by MITRE • 10/13/2026
Spoofing issue in the DOM: Web Serial component. This vulnerability was fixed in Firefox 158 and Firefox ESR 153.5.
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Analysis
by VulDB Data Team • 10/13/2026
The discovery of a spoofing vulnerability within the Document Object Model's Web Serial API highlights critical challenges in maintaining trust boundaries for hardware interface accessors in modern web browsers. The Web Serial component allows websites to communicate with serial devices, such as microcontrollers or industrial equipment, via USB-to-serial adapters. This functionality is inherently powerful and sensitive because it grants a webpage direct control over physical hardware interfaces that are typically reserved for native applications. When this API was introduced, the primary security concern revolved around user consent and explicit permission models to prevent unauthorized access. However, as browser implementations matured, new attack vectors emerged related to how these connections are presented to users during authentication prompts or status indicators.
The core technical flaw lies in a spoofing issue where an attacker could manipulate the visual representation of the serial connection request. Specifically, the vulnerability allowed for the deception of users regarding which origin was requesting access to a specific serial device. In standard browser security models, permission dialogs display the domain name and sometimes icons associated with the website seeking access. If these elements can be spoofed or misleadingly altered by malicious scripts, an attacker could craft a phishing scenario where a user believes they are granting permissions to a legitimate service while actually authorizing access for a malicious origin. This undermines the fundamental principle of least privilege and breaks the chain of trust between the user's intent and the actual system behavior.
From an operational impact perspective, this vulnerability poses significant risks in environments where serial devices control critical infrastructure or sensitive data processing units. An attacker leveraging this spoofing technique could trick users into granting persistent access to their hardware interfaces under false pretenses. Once granted, this access allows the malicious website to read data from connected sensors, send commands to actuators, or exfiltrate configuration details stored on microcontrollers like Arduino boards. The impact is particularly severe in Internet of Things deployments where web-based dashboards are used for monitoring and control, as it enables remote compromise of physical systems without requiring traditional software exploits or privilege escalation techniques.
This type of vulnerability aligns closely with CWE-201: Information Exposure Through Sent Data when the spoofing leads to unauthorized data retrieval, but more accurately maps to CWE-345: Insufficient Verification of Data Authenticity regarding the origin verification process during permission requests. In terms of offensive security frameworks, this behavior corresponds to MITRE ATT&CK technique T1608: Link Harvesting or potentially T1557: Adversary-in-the-Middle if used in conjunction with other phishing tactics to intercept credentials or session tokens associated with device management platforms. The attack vector is primarily classified under User Interaction requirements, meaning it relies on social engineering elements facilitated by the browser's UI deception capabilities rather than pure code execution flaws.
Mitigation strategies for this vulnerability focus heavily on enhancing user awareness and improving the clarity of permission dialogs. Browser vendors addressed this in Firefox 158 and Firefox ESR 153.5 by refining how origin information is displayed during serial device access requests, ensuring that domain names are rendered securely without susceptibility to CSS injection or DOM manipulation attacks that could alter their appearance. For developers integrating Web Serial APIs, it is crucial to implement robust validation of the user's intent through clear UI feedback and potentially multi-factor confirmation steps for high-risk operations. Additionally, organizations should restrict browser permissions on managed devices using group policies to limit which origins can request serial access, thereby reducing the attack surface even if a spoofing flaw were present in future versions. Regular auditing of web applications that utilize hardware interfaces against current security guidelines remains essential to prevent exploitation of such trust-based vulnerabilities.