Description

Privilege escalation due to incorrect boundary conditions in the Graphics: CanvasWebGL component. This vulnerability was fixed in Firefox 156, Firefox ESR 115.41, Firefox ESR 140.16, and Firefox ESR 153.3.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.8",
  "pubDate": "2026-09-15T13:16:48.357Z",
  "pubdate": "2026-09-15T13:16:48.357Z",
  "executiveSummary": "A privilege escalation vulnerability has been identified within the Graphics: CanvasWebGL component of the Mozilla Firefox browser. The flaw originates from incorrect boundary condition handling, which may allow a malicious actor to bypass security sandbox constraints.\nThe vulnerability affects Firefox 156, Firefox ESR 115.41, Firefox ESR 140.16, and Firefox ESR 153.3. By exploiting this defect, an attacker could potentially execute arbitrary code or gain elevated privileges on the underlying host operating system.\nThis issue represents a significant security risk, as it allows for sandbox escapes, effectively neutralizing the isolation layers designed to protect the user's system from compromised web content. Successful exploitation typically requires a victim to be lured into visiting a specially crafted malicious website that triggers the vulnerability through malformed WebGL operations.\nThe vulnerability does not require prior authentication, but does rely on the successful interaction with the browser's graphics rendering pipeline. Immediate remediation is required to mitigate the risk of remote code execution and unauthorized privilege escalation.",
  "technicalDetails": "The root cause of this vulnerability lies in an improper boundary check within the Graphics: CanvasWebGL component during the processing of specialized rendering commands. Specifically, the implementation fails to strictly validate the memory offsets or the size of data structures passed to the WebGL API buffers when performing complex coordinate or texture mapping operations.\nWhen the CanvasWebGL component receives a malformed request that exploits these incorrect boundary conditions, the browser's graphics engine may perform an out-of-bounds write or read operation. Because the WebGL component runs within the context of the content process, memory corruption at this stage can be leveraged to overwrite function pointers or manipulate internal browser objects.\nThe attack flow begins when an attacker directs a user to a malicious web page containing JavaScript designed to interact with the CanvasWebGL API. The attacker crafts a series of malicious WebGL commands—likely involving specifically sized vertex buffer objects or texture shaders—that force the engine to exceed its designated memory bounds. By carefully grooming the heap, an attacker can position controlled data in the memory adjacent to critical browser structures.\nUpon triggering the out-of-bounds memory access, the attacker can redirect control flow by overwriting return addresses or virtual method tables within the content process. Given that the browser sandbox enforces strict process isolation, this vulnerability is particularly potent as it provides the necessary primitive to break out of the content process sandbox. Once the sandbox is bypassed, the attacker achieves code execution with the privileges of the parent process or gains persistence within the host system, depending on the subsequent exploit chain.\nThe vulnerability is inherent to the logic processing WebGL operations and does not depend on user authentication. Exposure is strictly limited to the browser's handling of untrusted web content. The mitigation of this flaw requires patching the boundary logic within the graphics rendering component to ensure that all buffer accesses are strictly constrained and validated against the intended memory mapping."
}