CVE-2026-16375 | Site isolation issue in the Networking: HTTP component. This… | CVSS 9.8 CRITICAL

Description

Site isolation issue in the Networking: HTTP component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.

Metadata

CVE ID: CVE-2026-16375
State: PUBLISHED
Assigner: mozilla
Reserved: 2026-07-20 21:56 UTC
Published: 2026-07-21 12:37 UTC
Last updated: 2026-07-22 19:18 UTC
Primary CWE: CWE-346
CWE-346 Origin Validation Error
Vendor / Product: Mozilla / Firefox
Sources: cve.org · NVD

Severity & Metrics

9.8 CRITICAL CVSS 3.1

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

SSVC — CISA Coordinator

Exploitation: none
Automatable: yes
Tech. Impact: total

Affected products (2)

Vendor	Product	Platform	Versions
Mozilla	Firefox	—	140.13 ≤ 140., 153 ≤
Mozilla	Thunderbird	—	140.13 ≤ 140., 153 ≤

Weakness (CWE)

CWE	Source	Description
CWE-346	adp	CWE-346 Origin Validation Error

CVSS scores (1)

Score	Severity	Version	Source	Vector
9.8	CRITICAL	3.1	adp	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References (5)