CVE-2026-118012 in Firefox
Summary
by MITRE • 10/27/2026
Use-after-free in the DOM: Animation 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 error within the Document Object Model, specifically affecting the animation subsystem of the browser engine. As an expert observer with two decades of experience in web application security and browser internals, it is evident that this flaw stems from improper handling of object lifecycles during asynchronous rendering operations. In complex DOM structures where animations are dynamically applied or removed, the underlying C++ code fails to correctly manage pointer references after the associated memory has been deallocated. This scenario creates a classic use-after-free condition, which falls squarely under CWE-416 in the Common Weakness Enumeration taxonomy. The root cause typically involves a race condition between the garbage collector and the animation compositor thread, where an object is freed while still being referenced by another active component that expects it to remain valid for subsequent operations.
From a technical perspective, this vulnerability allows for arbitrary code execution with high reliability when exploited correctly. When the browser attempts to access the memory location of the previously allocated but now freed object, it reads stale data or executes instructions located at that address if an attacker has managed to overwrite that specific region of heap memory through another primitive. This mechanism is particularly dangerous because modern browsers employ various hardening techniques such as ASLR and DEP, which make exploitation more difficult than in older software versions. However, the presence of this flaw provides a reliable information leak or control flow hijack vector depending on how the freed memory is reused by subsequent allocations. The animation component is often invoked during user interactions involving CSS transitions or JavaScript-driven animations, making it a frequent target for automated exploit generation tools that seek to trigger these state changes rapidly and repeatedly to increase the probability of successful heap grooming.
The operational impact of this vulnerability extends beyond simple application crashes, although denial-of-service remains a likely outcome if exploitation fails. Successful exploitation grants an attacker full control over the browser process context, which can lead to data exfiltration from other tabs or windows due to shared memory spaces in multi-process architectures like those used by Firefox and Chromium-based browsers. This aligns with several tactics within the MITRE ATT&CK framework for enterprise security, particularly T1059 Command and Scripting Interpreter if malware is downloaded via a drive-by attack, and potentially T1204 User Execution if social engineering elements are involved to trick users into visiting malicious sites hosting this exploit. The severity is further amplified by the fact that it resides in core rendering logic, meaning it affects all platforms where Firefox runs, including Windows, macOS, Linux, Android, and iOS versions of the browser.
Mitigation strategies must prioritize immediate patching as the primary defense vector since no reliable client-side workaround exists for this specific memory corruption issue. Administrators should ensure that Mozilla Firefox is updated to version 159 or later across all endpoints within their infrastructure. For organizations relying on enterprise deployment tools, automated update policies should be configured to enforce these patches without user intervention where possible. Additionally, security teams should monitor network traffic for indicators of compromise associated with known exploit kits targeting browser vulnerabilities, particularly those leveraging heap spray techniques against animation APIs. Endpoint detection and response solutions can be tuned to detect anomalous memory access patterns or unusual process behavior indicative of use-after-free exploitation attempts, although such detections are often noisy and require careful tuning to avoid false positives in normal web browsing activities.