CVE-2026-117899 in Firefox
Summary
by MITRE • 10/27/2026
Use-after-free in the Networking: HTTP 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 • 10/28/2026
The identified vulnerability represents a critical memory management error classified as an out-of-bounds write within the Networking HTTP component of Mozilla Firefox browsers. This specific flaw is categorized under CWE-416, commonly known as Use After Free, which occurs when software continues to use a pointer after it has been freed or deallocated from system memory. In the context of web browser architecture, such vulnerabilities are particularly dangerous because they can be triggered by maliciously crafted web content that interacts with network requests and response handling mechanisms. The root cause typically involves a race condition or logic error where an object is released while still being referenced by another part of the application, leading to undefined behavior when the stale pointer is accessed.
From a technical perspective, this vulnerability allows for arbitrary code execution on the victim's system under certain conditions. When the browser processes HTTP traffic, it manages various objects related to connection states, headers, and body data. If an attacker can manipulate these operations such that memory associated with one object is freed while another process retains a reference to that same memory block, subsequent writes through that dangling pointer can overwrite adjacent heap metadata or other critical structures. This capability enables the exploitation of the vulnerability to gain control over program execution flow, potentially leading to remote code execution without any user interaction beyond visiting a malicious website or loading specific network resources.
The operational impact of this flaw is severe due to its potential for privilege escalation and system compromise. Since Firefox operates with the privileges of the end-user, successful exploitation could allow an attacker to execute arbitrary commands on the victim's machine. This can lead to data theft, installation of malware, or use of the compromised device as part of a botnet. The vulnerability affects multiple versions including Firefox 159 and specific Extended Support Release (ESR) channels such as ESR 115.44 and ESR 153.6, indicating that both standard users and enterprise environments relying on stable releases are at risk if they have not applied the latest security patches.
Mitigation strategies primarily involve immediate software updates to ensure all instances of Firefox are running versions where this issue has been resolved by Mozilla's engineering team. Organizations should enforce automated patch management policies for browser deployments, particularly in ESR channels which often lag behind standard release cycles but require strict adherence to security advisories. Additionally, deploying network-level controls such as Web Application Firewalls can help detect and block exploit attempts that attempt to trigger memory corruption through crafted HTTP requests. Users are advised to enable automatic updates where possible and remain vigilant against phishing campaigns designed to lure them into visiting malicious sites capable of triggering this vulnerability before patches are applied.