CVE-2026-109771 in Firefox
Summary
by MITRE • 10/13/2026
Information disclosure in the WebRTC: Networking component. This vulnerability was fixed in Firefox 158.
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Analysis
by VulDB Data Team • 10/13/2026
The identified vulnerability resides within the networking subsystem of Mozilla Firefox, specifically affecting components responsible for handling Web Real-Time Communication protocols. WebRTC is a framework that enables real-time communication capabilities such as audio and video conferencing directly between browsers without requiring plugins or additional software. The underlying architecture relies heavily on complex network interactions to establish connections, manage data streams, and handle NAT traversal techniques like STUN and TURN servers. In this specific instance, the flaw involves an improper handling of information within these networking operations, leading to a potential leak of sensitive internal state details that should remain isolated from external observers or untrusted contexts.
From a technical perspective, this issue classifies as an Information Disclosure vulnerability, which aligns with Common Weakness Enumeration identifier CWE-200: Exposure of Sensitive Information to an Unauthorized Actor. The root cause typically stems from insufficient validation or sanitization of data returned during network handshake processes or connection state queries. When the browser interacts with remote peers or local media devices through WebRTC APIs, it may inadvertently expose internal IP addresses, port numbers, protocol versions, or other metadata that can be leveraged by an attacker to map the victim's network topology. This exposure is particularly critical because modern browsers often run multiple tabs and applications simultaneously, increasing the attack surface for cross-origin data leakage if proper isolation boundaries are not strictly enforced during these low-level networking operations.
The operational impact of this vulnerability centers on privacy erosion and potential reconnaissance advantages for malicious actors. An attacker who can trigger or observe these network interactions could gather precise details about a user's local network environment, including private IP addresses that are normally hidden behind NAT gateways. This information is highly valuable in the context of cyber attacks as it facilitates more targeted subsequent exploits, such as internal port scanning or lateral movement within corporate networks if the victim is connected to an enterprise infrastructure. Furthermore, exposure of WebRTC-specific identifiers can aid in browser fingerprinting efforts, allowing attackers to create unique profiles for tracking users across different websites and sessions without their consent, thereby undermining user anonymity on the web.
In terms of threat modeling, this vulnerability maps to techniques observed in the MITRE ATT&CK framework, particularly those related to Discovery such as Network Service Scanning or System Information Discovery. While WebRTC is primarily designed for communication, its networking layer can be abused to probe internal services if the browser's security model fails to restrict access appropriately based on origin policies. The risk is amplified when users visit malicious websites that attempt to initiate WebRTC connections to extract local IP addresses via JavaScript APIs like getLocalAddresses or similar diagnostic functions exposed by the engine. This capability has been widely documented in privacy research as a significant vector for deanonymization, making its mitigation essential for maintaining user security and privacy standards.
Mozilla addressed this issue in Firefox version 158 through rigorous code audits and patching of the affected networking components. The fix likely involved strengthening input validation checks, enforcing stricter origin-based access controls on WebRTC APIs, or modifying how internal network state is exposed to JavaScript contexts. Users are strongly advised to update their browsers immediately to ensure they benefit from these security enhancements. Beyond software updates, administrators should enforce policies that restrict unnecessary use of real-time communication features in enterprise environments where possible and educate users about the privacy implications of granting media permissions to untrusted websites. Regular monitoring for unusual network activity originating from browser processes can also serve as an additional layer of defense against exploitation attempts targeting this class of vulnerabilities.