CVE-2026-8959

9.6 CRITICAL

Published: May 19, 2026 Modified: May 20, 2026

Description

Sandbox escape due to incorrect boundary conditions in the Widget: Win32 component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

AI Explanation

Get an AI-powered plain-language explanation of this vulnerability and remediation steps.

CVSS v3.x Details

0.0 Low Medium High Critical 10.0

Vector String

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

References to Advisories, Solutions, and Tools

Patch Vendor Advisory Exploit Third Party Advisory

https://bugzilla.mozilla.org/show_bug.cgi?id=2034754

Source: security@mozilla.org

Permissions Required

https://www.mozilla.org/security/advisories/mfsa2026-46/

Source: security@mozilla.org

Vendor Advisory

https://www.mozilla.org/security/advisories/mfsa2026-48/

Source: security@mozilla.org

Vendor Advisory

https://www.mozilla.org/security/advisories/mfsa2026-50/

Source: security@mozilla.org

Vendor Advisory

https://www.mozilla.org/security/advisories/mfsa2026-51/

Source: security@mozilla.org

Vendor Advisory

5 reference(s) from NVD

Quick Stats

CVSS v3 Score

9.6 / 10.0

EPSS (Exploit Probability)

0.2%

37th percentile

Exploitation Status

Not in CISA KEV

Weaknesses (CWE)

CWE-20 CWE-119 CWE-693

Affected Vendors

mozilla

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