CVE-2026-92010: Firefox CanvasWebGL Privilege Escalation

CVE-2026-92010 Overview

CVE-2026-92010 is a privilege escalation vulnerability in the Graphics: CanvasWebGL component of Mozilla Firefox and Thunderbird. The flaw stems from incorrect boundary conditions [CWE-120] in the WebGL rendering path used by the browser's canvas subsystem. An attacker who convinces a user to visit a malicious web page can trigger the boundary error and escalate privileges within the browser process. Mozilla addressed the issue in Firefox 156, Firefox ESR 115.41, Firefox ESR 140.16, Firefox ESR 153.3, Thunderbird 156, Thunderbird 140.16, and Thunderbird 153.3.

Critical Impact

Successful exploitation permits privilege escalation with high impact to confidentiality, integrity, and availability, and requires only that a user load attacker-controlled web content.

Affected Products

• Mozilla Firefox versions prior to 156
• Mozilla Firefox ESR versions prior to 115.41, 140.16, and 153.3
• Mozilla Thunderbird versions prior to 156, 140.16, and 153.3

Discovery Timeline

• 2026-09-15 - CVE-2026-92010 published to NVD
• 2026-09-16 - Last updated in NVD database

Technical Details for CVE-2026-92010

Vulnerability Analysis

The vulnerability resides in the Graphics: CanvasWebGL component, which implements the WebGL rendering pipeline exposed to web content through the HTML <canvas> element. Incorrect boundary conditions in this component allow memory operations to occur outside intended limits during graphics processing. Because WebGL directly manipulates GPU buffers and shader inputs from JavaScript, mishandled boundary checks translate into memory safety violations reachable from any origin.

Exploitation requires user interaction, typically loading a crafted page or opening HTML email content rendered by Thunderbird. Once triggered, the flaw enables privilege escalation within the browser's execution context, potentially undermining process isolation and sandbox boundaries.

Root Cause

The underlying weakness is classified as [CWE-120] Buffer Copy without Checking Size of Input. Mozilla's advisories describe the defect as an incorrect boundary condition in CanvasWebGL, meaning the component fails to properly validate size or offset parameters before performing memory operations on graphics buffers. Details are tracked in Mozilla Bug Report #2058067.

Attack Vector

The attack vector is network-based and requires user interaction. An attacker hosts malicious JavaScript that invokes specific WebGL APIs with parameters designed to bypass boundary checks. When a victim visits the page in a vulnerable Firefox build, or previews an HTML message in vulnerable Thunderbird, the CanvasWebGL code path processes the attacker-supplied data and corrupts memory, enabling privilege escalation within the browser.

No public proof-of-concept exploit is currently listed for this CVE. Refer to the Mozilla Security Advisory MFSA-2026-90 series for vendor technical details.

Detection Methods for CVE-2026-92010

Indicators of Compromise

• Firefox or Thunderbird processes crashing or spawning unexpected child processes shortly after loading web or HTML email content.
• Outbound connections from browser processes to previously unseen domains hosting WebGL-heavy pages.
• Unexpected file writes or process launches originating from firefox.exe, firefox, or thunderbird binaries running below patched versions.

Detection Strategies

• Inventory endpoints for Firefox and Thunderbird versions and flag any installations below Firefox 156, ESR 115.41, ESR 140.16, ESR 153.3, or the corresponding Thunderbird builds.
• Monitor endpoint telemetry for anomalous child processes or shellcode-like behavior chained from browser processes.
• Correlate web proxy logs with browser crash telemetry to identify pages that consistently precede browser instability.

Monitoring Recommendations

• Enable browser crash reporting and forward reports to a central analytics pipeline for triage.
• Alert on browser processes performing unusual actions such as writing to autostart locations or loading unsigned modules.
• Track WebGL-heavy domains accessed by users still running unpatched browser builds.

How to Mitigate CVE-2026-92010

Immediate Actions Required

• Upgrade Firefox to version 156 or later on all managed endpoints.
• Upgrade Firefox ESR deployments to 115.41, 140.16, or 153.3 depending on the branch in use.
• Upgrade Thunderbird to 156, 140.16, or 153.3 to protect users who render HTML email content.
• Prioritize systems where users routinely browse untrusted web content or open external email.

Patch Information

Mozilla addressed CVE-2026-92010 across the Firefox and Thunderbird release trains. Consult Mozilla Security Advisory MFSA-2026-90, MFSA-2026-91, MFSA-2026-92, MFSA-2026-93, MFSA-2026-94, MFSA-2026-95, and MFSA-2026-96 for advisory-to-product mapping.

Workarounds

• Disable WebGL in Firefox by setting webgl.disabled to true in about:config where patching is temporarily blocked.
• Configure Thunderbird to display messages as plain text to reduce exposure to malicious HTML rendering.
• Restrict browsing to trusted sites via web filtering or enterprise policy until patched builds are deployed.

# Firefox enterprise policy example: disable WebGL until patching completes
# policies.json (Windows: %ProgramFiles%\Mozilla Firefox\distribution\)
{
  "policies": {
    "Preferences": {
      "webgl.disabled": {
        "Value": true,
        "Status": "locked"
      }
    }
  }
}