Description

Privilege escalation due to use-after-free in the Graphics: Canvas2D component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, and Firefox ESR 153.1.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.8",
  "pubDate": "2026-08-18T13:17:31.683Z",
  "pubdate": "2026-08-18T13:17:31.683Z",
  "executiveSummary": "A use-after-free vulnerability exists in the Graphics: Canvas2D component of Mozilla Firefox, leading to potential privilege escalation. This memory corruption flaw impacts Firefox, Firefox ESR 140, and Firefox ESR 153. Successful exploitation of this vulnerability allows an attacker to execute arbitrary code or compromise the integrity of the browser environment. The flaw arises from improper memory management within the rendering engine when handling Canvas2D operations. Risk implications include unauthorized system access and potential sandbox escapes, depending on attacker capabilities and system configurations. Exploitation typically requires the victim to interact with malicious web content, such as navigating to a crafted webpage containing malicious scripts designed to trigger the use-after-free condition. No specific authentication is required for initial exploitation over the network channel, presenting a significant threat vector to unpatched systems across enterprise and consumer environments.",
  "technicalDetails": "The vulnerability is a classic use-after-free (UAF) condition residing within the Graphics: Canvas2D component of the Mozilla Firefox browser. The root cause stems from a flaw in memory management and object lifecycle tracking within the rendering pipeline, specifically when asynchronous or synchronous operations manipulate Canvas2D rendering contexts and associated memory buffers. When an object is prematurely freed or its reference count is improperly handled, subsequent references to the deallocated memory block persist. If an attacker can predictably manipulate the heap layout and trigger a re-allocation of the freed memory region with attacker-controlled data (heap feng-shui), dereferencing the dangling pointer results in arbitrary code execution within the context of the affected process.\nThe affected versions include Firefox prior to version 154, Firefox ESR prior to version 140.14, and Firefox ESR prior to version 153.1. The vulnerable component is strictly tied to the Graphics: Canvas2D engine. Network exposure is present in the sense that the attack vector is exploitable remotely via standard web browsing; an attacker requires a victim to load a malicious web page hosting crafted JavaScript code interacting with the Canvas2D API. Privilege requirements for the initial trigger are minimal, as standard unauthenticated web content execution is sufficient to interact with the vulnerable APIs. Post-exploitation impact can range from arbitrary code execution within the browser's security sandbox to full system privilege escalation if chaining with additional vulnerabilities or sandbox escape vectors is achieved. The attack flow proceeds as follows: 1) The attacker constructs a malicious webpage containing specialized JavaScript targeting Canvas2D objects. 2) The victim visits the page using an unpatched version of Firefox. 3) The browser's Graphics: Canvas2D component processes the script, triggering a sequence that releases a memory object while retaining a dangling pointer. 4) The attacker forces heap spraying or memory reuse to populate the freed chunk with controlled payload structures. 5) The application accesses the dangling pointer, executing the attacker's payload and achieving privilege escalation or arbitrary code execution."
}