CVE-2026-117987 in Firefox
Summary
by MITRE • 10/27/2026
Use-after-free in the Graphics component. This vulnerability was fixed in Firefox 159 and Firefox ESR 153.6.
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Analysis
by VulDB Data Team • 10/27/2026
The identified security issue represents a critical memory management flaw within the graphics subsystem of Mozilla Firefox, specifically classified as an out-of-bounds write resulting from a use-after-free condition. This type of vulnerability arises when software continues to utilize a pointer after the memory it references has been deallocated or freed by the system. In the context of browser-based rendering engines such as Gecko, which handles complex graphical operations including canvas drawing, WebGL contexts, and CSS animations, precise lifecycle management of graphic objects is paramount. When an object representing a graphics resource is destroyed but retained in memory through lingering references held by other components, subsequent access to that stale pointer leads to undefined behavior. The specific manifestation here involves writing data to this invalid memory location, which constitutes an out-of-bounds write rather than merely reading sensitive information. This distinction is crucial because writes allow for potential control over program execution flow or corruption of adjacent heap structures, significantly escalating the severity from a simple information disclosure risk to one capable of arbitrary code execution under the right conditions.
From a technical perspective, this vulnerability aligns with Common Weakness Enumeration identifier CWE-416, which defines use-after-free errors as a category where pointers are used after they have been freed. The operational impact of such a flaw is severe because browsers operate in highly dynamic environments where memory allocation and deallocation occur frequently during page rendering and script execution. An attacker could craft a malicious webpage containing specially designed JavaScript code or embedded graphics resources that trigger the premature freeing of a graphic object while maintaining active references to it within the browser's internal state machines. By carefully controlling heap layout through repeated allocations, an adversary might achieve arbitrary read-write primitives, allowing them to overwrite function pointers in virtual tables or manipulate critical data structures such as exception handlers. This capability effectively bypasses modern memory protection mechanisms like Data Execution Prevention and Address Space Layout Randomization if exploited with sufficient precision, leading to full system compromise on the victim's machine.
The vulnerability is further contextualized within the MITRE ATT&CK framework under techniques related to exploitation for privilege escalation or initial access via browser-based attacks. Specifically, it falls under T1203 Exploitation for Client Execution and potentially relates to heap spraying methodologies often employed in drive-by download scenarios. The graphics component serves as a high-value target because it processes untrusted input from web content directly into binary operations that interact with the operating system's display drivers or GPU APIs. A successful exploit could allow malicious actors to execute code within the browser process context, which may then be leveraged for further lateral movement if sandboxing mechanisms are bypassed or misconfigured. The presence of such a flaw underscores the complexity inherent in managing shared resources across multiple threads and processes within a modern web browser architecture, where race conditions between garbage collection routines and rendering pipelines can create narrow windows for exploitation.
Mitigation strategies primarily rely on timely software updates to apply the fixes introduced in Firefox version 159 and Firefox Extended Support Release (ESR) version 153.6. These patches likely involve rigorous validation of pointer lifecycles, ensuring that references are nullified immediately upon deallocation or implementing smart pointers with automatic reference counting to prevent premature freeing. Organizations should enforce automated patch management policies to ensure all endpoints running affected versions are updated promptly. Additionally, deploying browser hardening configurations such as disabling JavaScript in untrusted zones or utilizing content security policies can reduce the attack surface available to potential exploiters. Security teams must also monitor for indicators of compromise associated with drive-by download campaigns targeting outdated browsers and conduct regular vulnerability assessments to identify any lingering instances of unsupported software versions within their infrastructure.