Description
Sandbox escape due to incorrect boundary conditions in the Graphics: WebRender component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.
Published: 2026-09-29
Score: 9.6 Critical
EPSS: < 1% Very Low
KEV: No
Impact: Sandbox Escape
Action: Patch Now
AI Analysis

Impact

This vulnerability describes a sandbox escape in Mozilla’s Graphics: WebRender component caused by incorrect boundary checks. An attacker could trigger the flaw by supplying malicious graphic content, which would allow execution with the privileges of the browser process.

Affected Systems

All Firefox and Thunderbird users running versions earlier than Firefox 157, Firefox ESR 115.42, Firefox ESR 140.17, Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, or Thunderbird 153.4 are affected. This includes every operating system supported by those releases.

Risk and Exploitability

Exploit would require loading crafted graphics into the browser; once triggered, the sandbox escape could lead to arbitrary code execution. The CVSS score of 9.6 reflects a critical severity, and the EPSS score of < 1% indicates a very low likelihood of exploitation, and the vulnerability is not listed in the CISA KEV catalog.

Generated by OpenCVE AI on October 1, 2026 at 18:11 UTC.

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

  • Upgrade to Firefox 157 or newer, or to any newer ESR release (115.42, 140.17, or 153.4).
  • If updating is not immediately possible, disable the WebRender engine by setting the preference dom.webrender.enabled to false in about:config.
  • Consider running Firefox inside a sandboxed container to contain any potential exploitation.

Generated by OpenCVE AI on October 1, 2026 at 18:11 UTC.

Tracking

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Advisories
Source ID Title
Debian DLA Debian DLA DLA-4810-1 thunderbird security update
Debian DLA Debian DLA DLA-4814-1 firefox-esr security update
Debian DSA Debian DSA DSA-6533-1 firefox-esr security update
Debian DSA Debian DSA DSA-6536-1 thunderbird security update
History

Mon, 05 Oct 2026 15:15:00 +0000

Type Values Removed Values Added
First Time appeared Mozilla thunderbird
CPEs cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*
cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*
Vendors & Products Mozilla thunderbird

Thu, 01 Oct 2026 17:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Thu, 01 Oct 2026 16:30:00 +0000

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 9.6, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H'}

Thu, 01 Oct 2026 04:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-119

Thu, 01 Oct 2026 02:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-787

Wed, 30 Sep 2026 17:45:00 +0000

Type Values Removed Values Added
Description Sandbox escape due to incorrect boundary conditions in the Graphics: WebRender component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17. Sandbox escape due to incorrect boundary conditions in the Graphics: WebRender component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.
References

Wed, 30 Sep 2026 17:30:00 +0000

Type Values Removed Values Added
Description Sandbox escape due to incorrect boundary conditions in the Graphics: WebRender component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17. Sandbox escape due to incorrect boundary conditions in the Graphics: WebRender component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.
References

Wed, 30 Sep 2026 09:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-787

Wed, 30 Sep 2026 03:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-119

Tue, 29 Sep 2026 17:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-119

Tue, 29 Sep 2026 16:45:00 +0000

Type Values Removed Values Added
First Time appeared Mozilla
Mozilla firefox
Vendors & Products Mozilla
Mozilla firefox

Tue, 29 Sep 2026 13:15:00 +0000

Type Values Removed Values Added
Description Sandbox escape due to incorrect boundary conditions in the Graphics: WebRender component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.
Title Sandbox escape due to incorrect boundary conditions in the Graphics: WebRender component
References

Subscriptions

Mozilla Firefox Thunderbird
cve-icon MITRE

Status: PUBLISHED

Assigner: mozilla

Published:

Updated: 2026-10-01T15:30:44.116Z

Reserved: 2026-09-26T19:16:55.886Z

Link: CVE-2026-100781

cve-icon Vulnrichment

Updated: 2026-10-01T15:30:33.679Z

cve-icon NVD

Status : Analyzed

Published: 2026-09-29T13:17:43.023

Modified: 2026-10-05T15:01:33.840

Link: CVE-2026-100781

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-01T18:15:10Z

Weaknesses
  • CWE-119

    Improper Restriction of Operations within the Bounds of a Memory Buffer