CVE-2026-117908 in Firefox
Summary
by MITRE • 10/27/2026
Use-after-free in the Graphics: ImageLib 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 within Mozilla's image processing subsystem, specifically located in the ImageLib component which handles the decoding and rendering of various graphic formats such as JPEG, PNG, GIF, and WebP. This flaw is classified technically as an use-after-free condition, corresponding to CWE-416 in the Common Weakness Enumeration taxonomy. In this scenario, a pointer to a memory block that has already been deallocated or freed by the system continues to be referenced and accessed by the application logic. The root cause typically stems from improper lifecycle management of objects within the asynchronous image decoding pipeline, where an object is destroyed while still being held in reference by another active process or thread that expects it to remain valid for subsequent operations.
From a technical perspective, when Firefox processes complex or malformed image data, it allocates specific memory structures to manage metadata and pixel buffers. If the application logic fails to properly synchronize access between threads or neglects to nullify pointers after deletion, the program may attempt to read from or write to that now-invalid memory address. This can lead to unpredictable behavior ranging from visual artifacts in rendered images to more severe consequences such as application crashes due to segmentation faults. In worst-case scenarios involving carefully crafted malicious image files, an attacker could potentially leverage this instability to execute arbitrary code with the privileges of the user running the browser, although modern exploit mitigation techniques like ASLR and DEP significantly raise the bar for successful exploitation.
The operational impact of this vulnerability is primarily centered on stability and potential security compromise during normal browsing activities that involve loading images from untrusted sources. Since image processing occurs frequently in web pages containing rich media content, users are exposed to risk simply by visiting compromised or maliciously designed websites. The lack of robust bounds checking or reference counting errors allows for memory corruption which can be exploited to bypass sandboxing mechanisms if the vulnerability is chained with other flaws. This underscores the importance of rigorous memory safety practices within high-performance components like ImageLib that handle large volumes of external data input.
Mitigation strategies focus on both immediate patching and long-term architectural improvements. The primary defense is applying the security update provided in Firefox version 159, as well as the extended support release versions 115.44 and 153.6, which contain specific code changes to correct the reference counting logic and ensure that pointers are invalidated immediately after memory deallocation. For organizations managing large fleets of browsers, automated deployment tools should be utilized to enforce these updates promptly. Additionally, developers can mitigate similar risks by adopting safer programming practices such as using smart pointers in C++ development or leveraging Rust for new components to eliminate manual memory management errors entirely. Regular security audits and fuzzing tests targeting the image decoding libraries are also recommended to detect edge cases before they reach production environments.