Description

Privilege escalation due to incorrect boundary conditions in the Graphics: WebRender 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": "2026-09-15T13:16:51.990Z",
  "pubdate": "2026-09-15T13:16:51.990Z",
  "executiveSummary": "A privilege escalation vulnerability exists within the Graphics: WebRender component of the Mozilla Firefox browser. The flaw arises from incorrect handling of boundary conditions during graphics rendering operations.\nSuccessful exploitation allows a local attacker to execute arbitrary code or escalate privileges within the context of the application. This vulnerability poses a significant risk to system integrity and user security, as it bypasses standard browser sandbox protections.\nThe vulnerability affects Firefox 156, Firefox ESR 115.41, Firefox ESR 140.16, and Firefox ESR 153.3. Exploitation typically requires the victim to render malicious content, such as a specially crafted webpage, which triggers the out-of-bounds access.\nAttacker capabilities include potential memory corruption, which can lead to unauthorized access to system resources. No specialized authentication is required, but the attacker must be able to influence the input processed by the graphics engine.",
  "technicalDetails": "The vulnerability resides in the WebRender component, which is responsible for rendering web content using the GPU. The root cause is a boundary condition error occurring during memory management or buffer operations when processing complex graphics data.\nWhen WebRender attempts to process malformed or specifically crafted graphical input, it fails to perform adequate bounds checking before accessing memory regions. This leads to an out-of-bounds (OOB) memory access, specifically manifesting as a read or write operation beyond the allocated buffer boundaries.\nThe attack flow initiates when the browser processes malicious content that leverages the WebRender graphics pipeline. By supplying a specially crafted payload—such as an exploit targeting the GPU process communication or shared memory buffers—the attacker can trigger the incorrect boundary condition logic.\nSince WebRender operations often occur within high-privilege or sandboxed browser processes, the OOB access can be leveraged to overwrite critical control structures, such as function pointers or return addresses stored on the heap or stack. This memory corruption can facilitate the redirection of the execution flow to arbitrary code, potentially bypassing memory protection mechanisms like ASLR (Address Space Layout Randomization) and DEP (Data Execution Prevention).\nOnce the execution flow is successfully hijacked, the attacker can execute code with the privileges of the affected browser process. Given the architecture of modern browsers, escalating from a renderer or GPU process to a higher-privilege context (such as the main parent process) is a common objective for post-exploitation activities, including persistence or data exfiltration.\nThis vulnerability is classified as a privilege escalation issue because the boundary condition flaw allows an attacker to break out of the restricted execution environment. The flaw affects versions Firefox 156, Firefox ESR 115.41, Firefox ESR 140.16, and Firefox ESR 153.3, which contain the necessary logic to enforce correct boundary checks upon remediation.\nThe exploit does not require prior authentication from the user, but relies on the browser's interaction with the malicious graphics state. The failure to validate input lengths and buffer offsets represents a fundamental oversight in the graphics subsystem's memory safety controls."
}