CVE-2026-8959

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.

CVSS v3 9.6 CRITICAL

9.6^/10

CVSS v3 : CRITICAL

Vector :

Exploitability : 2.8 / Impact : 6.0

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction REQUIRED

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact HIGH

Scope CHANGED

References

Link	Resource
https://bugzilla.mozilla.org/show_bug.cgi?id=2034754	Permissions Required
https://www.mozilla.org/security/advisories/mfsa2026-46/	Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-48/	Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-50/	Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-51/	Vendor Advisory

Configurations

Configuration 1 (hide)

OR	cpe:2.3:a:mozilla:firefox:::::esr:::*
	cpe:2.3:a:mozilla:firefox:::::-:::*
	cpe:2.3:a:mozilla:thunderbird:::::esr:::*
	cpe:2.3:a:mozilla:thunderbird::::::::

History

No history.

Information

Published : 2026-05-19 14:16

Updated : 2026-06-17 11:04

NVD link : CVE-2026-8959

Mitre link : CVE-2026-8959

CVE.ORG link : CVE-2026-8959

JSON object : View

Products Affected

mozilla

thunderbird
firefox

CWE

CWE-20

Improper Input Validation

CWE-119

Improper Restriction of Operations within the Bounds of a Memory Buffer

CWE-693

Protection Mechanism Failure

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