CVE-2026-117907 in Firefox
Summary
by MITRE • 10/27/2026
Use-after-free in the 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 vulnerability represents a critical memory management error classified as an out-of-bounds write resulting from a use-after-free condition within the Networking component of Mozilla Firefox browsers. This specific flaw occurs when the application attempts to access or manipulate a block of memory that has already been deallocated by the system's garbage collector or explicit free operations. In complex web environments, network requests often trigger asynchronous callbacks and event handlers that manage resource lifecycles dynamically. If the reference counting mechanism fails to properly synchronize these events with the actual release of network buffers, an attacker can exploit a race condition where the memory is freed while still being referenced by active networking threads or JavaScript execution contexts. This scenario allows for arbitrary read and write operations in memory space previously owned by the browser process, fundamentally compromising the integrity of the application's data structures.
From a technical perspective, this vulnerability aligns with Common Weakness Enumeration identifier CWE-416, which describes use-after-free errors that lead to undefined behavior and potential code execution. The exploitation vector typically involves crafting malicious web content or manipulating network responses in a way that triggers the premature deallocation of critical networking objects while they are still being accessed by subsequent operations. This could involve sending specially crafted HTTP headers, WebSocket frames, or triggering specific DNS resolution paths that cause internal buffers to be released prematurely. Because modern browsers operate with multiple processes and sandboxing mechanisms, successfully exploiting this flaw requires bypassing these isolation layers through precise memory corruption techniques such as heap spraying or type confusion attacks to gain control over the instruction pointer or data pointers within the browser process context.
The operational impact of a successful exploitation is severe, potentially leading to arbitrary code execution on the victim's system with the privileges of the current user. An attacker could leverage this vulnerability to install malware, exfiltrate sensitive browsing history and cookies, hijack active sessions for web applications including banking or email services, or use the compromised browser as a pivot point for further network attacks. The risk is particularly acute given that Firefox users frequently engage with untrusted websites, making them susceptible to drive-by download attempts or malicious script injections designed specifically to trigger this memory corruption flaw. Furthermore, because networking components are central to almost all web interactions, the attack surface remains broad and difficult to mitigate through simple user behavior changes alone.
Mitigation strategies primarily rely on applying the vendor-provided security patches immediately upon availability. Users must ensure they have upgraded to Firefox version 159 or later, as well as the extended support release versions 115.44 and 153.6 where applicable for enterprise environments. In addition to patching, organizations should enforce strict content security policies that restrict inline scripts and unauthorized external resources to reduce the likelihood of triggering malicious payloads in the first place. Deploying browser isolation technologies or sandboxed browsing profiles can further limit the blast radius if a vulnerability is exploited by restricting the permissions granted to the browser process. Continuous monitoring for anomalous network activity and memory usage patterns within endpoint detection systems may also aid in identifying attempted exploitation activities before full compromise occurs, aligning with ATT&CK techniques related to initial access via web delivery and defense evasion through memory manipulation.