CVE-2026-100809

HIGH CVSS 3.1: 8.1 EPSS 0.15%
Updated Oct 05, 2026
Firefox
Parameter Value
CVSS 8.1 (HIGH)
Affected Versions 154.0 — 157.0.0
Fixed In 153.4.0
Type CWE-346 (Origin Validation Error)
Vendor Firefox
Public PoC No

Same-origin policy bypass in the DevTools component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157.

Attack Parameters

Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
Required
User action required

Impact Assessment

Confidentiality
High
Complete data leak
Integrity
High
Complete data modification
Availability
None
No disruption

CVSS Vector v3.1

Vulnerable Products 4

Configuration From (including) Up to (excluding)
Mozilla Firefox
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
— 153.4.0
Mozilla Firefox
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
154.0.0 157.0.0
Mozilla Thunderbird
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*
— 153.4.0
Mozilla Thunderbird
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*
154.0 157.0