CVE-2026-117892 in Firefox
Summary
by MITRE • 10/27/2026
Privilege escalation due to use-after-free in the WebRTC: Networking component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6.
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Analysis
by VulDB Data Team • 10/27/2026
The identified security flaw resides within the WebRTC networking subsystem of Mozilla Firefox, specifically manifesting as a use-after-free condition that enables privilege escalation. This type of vulnerability arises from improper memory management practices where the application continues to reference a block of memory after it has been freed or deallocated by the system. In the context of browser-based technologies like WebRTC, which handles real-time audio and video communication over complex network stacks, such errors can be particularly dangerous because they allow an attacker who successfully exploits this flaw to execute arbitrary code within the security sandbox of the browser process. The severity is amplified by the fact that successful exploitation typically grants the attacker a level of access equivalent to the current user, potentially leading to full system compromise if combined with other local vulnerabilities or misconfigurations.
From a technical perspective, use-after-free errors often occur when pointers are not properly nullified after memory release, or when reference counting mechanisms fail to track object lifecycles accurately during asynchronous network operations. In WebRTC's networking layer, this could involve race conditions where one thread frees an object while another thread attempts to access it before the garbage collector or manual cleanup can complete its task. This creates a window of opportunity for heap corruption, which attackers leverage to overwrite adjacent memory structures with malicious payloads. The exploitation path typically involves crafting specific network packets or manipulating WebRTC signaling data to trigger the premature deallocation followed by immediate reuse under attacker-controlled conditions.
The operational impact of this vulnerability is significant due to its potential for remote code execution via a web page. An attacker could host a specially crafted website that, when visited by an unsuspecting user, triggers the vulnerable code path within their browser. If successful, the malicious script gains elevated privileges beyond the intended sandbox restrictions. This compromises not only the confidentiality and integrity of the browsing session but also poses risks to sensitive data stored locally on the victim's machine or accessed through authenticated sessions with other services. The ability to escalate privileges means that standard web isolation mechanisms are bypassed, allowing lateral movement within the user environment.
Industry standards classify this flaw under CWE-416, which defines use-after-free as a critical memory safety issue. Furthermore, in terms of attack tactics and techniques, this vulnerability aligns with MITRE ATT&CK technique T1203, specifically relating to exploitation for defense evasion or privilege escalation through client-side software vulnerabilities. The fix implemented in Firefox version 159, along with the corresponding updates for Firefox ESR versions 115.44 and 153.6, addresses these memory management defects by ensuring proper lifecycle tracking of network objects and preventing access to freed memory regions.
To mitigate the risks associated with such vulnerabilities, users must ensure their browsers are updated to the latest stable or extended support release as soon as possible. For organizations relying on Firefox ESR versions, it is crucial to monitor Mozilla's security advisories closely to apply patches promptly without disrupting long-term stability goals. Additionally, implementing strict content security policies and disabling unnecessary WebRTC features in environments where real-time communication is not required can reduce the attack surface. Security teams should also consider deploying browser isolation technologies or sandboxing solutions that further restrict the potential impact of any successful exploitation attempt, ensuring that even if a vulnerability like this were to be exploited, its effects remain contained within isolated processes rather than affecting the broader system.