CVE-2026-118006 in Firefox
Summary
by MITRE • 10/27/2026
Privilege escalation due to 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 flaw within the signaling subsystem of Mozilla's WebRTC implementation, specifically categorized as an out-of-bounds write resulting from a use-after-free condition. In complex web communication frameworks like WebRTC, the signaling component is responsible for managing session negotiation protocols such as Session Description Protocol (SDP) and Interactive Connectivity Establishment (ICE). These processes involve dynamic allocation and deallocation of memory structures that track connection states, candidate pairs, and media descriptions. The root cause lies in a failure to properly invalidate pointers or nullify references after the underlying data structure has been freed by the garbage collector or explicit deletion routines. Consequently, subsequent operations within the signaling pipeline may attempt to access or modify this previously released memory block, leading to an out-of-bounds write operation where arbitrary data is written to unintended memory locations adjacent to the original allocation.
From a technical perspective, use-after-free vulnerabilities are among the most dangerous classes of software defects because they provide attackers with significant control over program execution flow and memory state. When the signaling component processes malformed or specially crafted SDP messages during a WebRTC session setup, it may trigger a sequence where an object is destroyed while still referenced by another active part of the system. The subsequent write operation allows for heap corruption, which can be exploited to overwrite function pointers, virtual table entries, or other critical control data structures within the browser process memory space. This mechanism bypasses standard sandboxing protections if the attacker can achieve sufficient precision in their memory layout manipulation, potentially leading to arbitrary code execution with the privileges of the compromised user account.
The operational impact of this vulnerability is severe, as it affects any web application or website that utilizes WebRTC for real-time audio, video, or data communication. An adversary hosting a malicious webpage could craft specific signaling payloads designed to trigger the use-after-free condition when visited by an unsuspecting user. Successful exploitation would allow the attacker to execute arbitrary code on the victim's machine, facilitating actions such as installing malware, stealing sensitive credentials stored in browser memory, capturing keystrokes or screen contents via WebRTC APIs, or pivoting further into internal networks if the browser has access to local resources. Given that Firefox is a widely used general-purpose web browser, this vulnerability poses a risk to a broad user base relying on secure and stable browsing experiences for both personal and professional communications.
Mitigation strategies primarily involve applying the vendor-provided patch included in Firefox version 159, which addresses the memory management logic by ensuring proper pointer invalidation and reference counting adjustments within the signaling module. Users should immediately update their browsers to this patched version or later releases where similar hardening measures have been applied across related components. For organizations deploying Firefox through enterprise policies, it is essential to enforce automatic updates or deploy patching scripts via centralized configuration management tools like Microsoft Endpoint Manager or Ansible to ensure all endpoints are protected against exploitation attempts. Additionally, security teams should monitor for indicators of compromise associated with WebRTC-based attacks and consider implementing browser-level restrictions on WebRTC permissions for untrusted domains where real-time communication is not required, thereby reducing the attack surface available to potential exploiters.
This vulnerability aligns with Common Weakness Enumeration identifier CWE-416, which describes use-after-free conditions, a category of errors that frequently lead to memory corruption and privilege escalation in modern software systems. In terms of tactical mapping within the MITRE ATT&CK framework, this flaw facilitates initial access through drive-by compromise techniques under Tactic TA0001 and enables execution via exploitation for binary patching or arbitrary code execution under Technique T1203. The reliance on dynamic memory management without adequate safeguards highlights the importance of rigorous static analysis tools and fuzz testing during the development lifecycle to detect such logic errors before they reach production environments, ensuring that critical infrastructure components like browser engines remain resilient against sophisticated memory corruption attacks.