CVE-2026-118005 in Firefox
Summary
by MITRE • 10/27/2026
Use-after-free in the WebRTC: Signaling component. This vulnerability was fixed in Firefox 159.
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Analysis
by VulDB Data Team • 10/27/2026
The identified vulnerability represents a critical memory management error within the signaling subsystem of Mozilla's WebRTC implementation, specifically classified as an out-of-bounds write resulting from use-after-free conditions. In complex web communication frameworks like WebRTC, the signaling component is responsible for managing session control messages that establish, modify, and terminate peer-to-peer connections. This process involves intricate object lifecycle management where pointers to data structures are passed between various handlers and asynchronous callbacks. The flaw arises when a pointer to an already freed memory block remains accessible within the application's execution context due to improper reference counting or missing nullification of dangling pointers after deallocation. When subsequent operations attempt to write data through this stale pointer, they inadvertently overwrite adjacent memory regions rather than allocating new space for valid objects. This behavior constitutes a classic use-after-free vulnerability which is widely recognized in security taxonomy as CWE-416, indicating that the software continues to use references to memory after it has been freed leading to unpredictable system states and potential exploitation vectors.
From an operational perspective, this type of memory corruption poses severe risks beyond simple application crashes or denial-of-service scenarios. Because the vulnerability allows for arbitrary write operations within the process memory space, a malicious actor can craft specific signaling payloads designed to manipulate heap structures during the overwrite phase. By carefully controlling the contents written into the freed memory region, an attacker may achieve code execution capabilities on the victim's machine. This aligns with ATT&CK technique T1203 which covers exploitation for client-side attacks where software vulnerabilities are leveraged to execute malicious commands without user interaction beyond visiting a compromised webpage or receiving a crafted media session invitation. The severity is further amplified by the fact that WebRTC operates at a low level within the browser engine, granting potential attackers access to sensitive APIs related to microphone and camera capture as well as direct network socket manipulation if privilege escalation occurs through other means.
The remediation strategy implemented in Firefox version 159 addresses this issue by enforcing stricter memory safety protocols within the signaling module. The fix likely involves introducing additional checks during object destruction sequences to ensure that all references are invalidated immediately upon deallocation, thereby preventing any subsequent access attempts from succeeding. Additionally, modern browser engines increasingly rely on Rust-based components for critical infrastructure parts like WebRTC to provide compile-time guarantees against such memory safety violations. For system administrators and developers relying on older versions of Firefox or other browsers with similar implementations, immediate patching is essential to mitigate the risk of remote code execution via malicious web content. Users should ensure their browser software is updated to the latest stable release which incorporates these security patches. Furthermore, employing strict Content Security Policies can help limit the impact by restricting the sources from which WebRTC connections are initiated and signaling data is accepted, adding a layer of defense-in-depth against exploitation attempts targeting this specific flaw in the media handling pipeline.