CVE-2026-84140
published 2026-09-01CVE-2026-84140: Site isolation issue in the DOM: Navigation component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
PriorityP352critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
EPSS
0.18%
7.4th percentile
Site isolation issue in the DOM: Navigation component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
Affected
8 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| mozilla | firefox | < Firefox 155 | Firefox 155 |
| mozilla | firefox | < 153.2.0 | 153.2.0 |
| mozilla | firefox | >= 154.0.0 < 155.0.0 | 155.0.0 |
| mozilla | firefox_esr | < Firefox ESR 153.2 | Firefox ESR 153.2 |
| mozilla | thunderbird | < Thunderbird 155 | Thunderbird 155 |
| mozilla | thunderbird | < Thunderbird 153.2 | Thunderbird 153.2 |
| mozilla | thunderbird | < 153.2.0 | 153.2.0 |
| mozilla | thunderbird | >= 154.0 < 155.0 | 155.0 |
CVSS provenance
nvdv3.19.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
vendor_redhat9.8CRITICAL
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Red Hat
firefox: thunderbird: Site isolation issue in the DOM: Navigation component
vendor_redhat·2026-09-01·CVSS 9.8
CVE-2026-84140 [CRITICAL] CWE-1100 firefox: thunderbird: Site isolation issue in the DOM: Navigation component
firefox: thunderbird: Site isolation issue in the DOM: Navigation component
Site isolation issue in the DOM: Navigation component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue:
Site isolation issue in the DOM: Navigation component
Statement: Red Hat Product Security rates the severity of this flaw as determined by the Mozilla Foundation Security Advisory.
Mitigation: Update to Firefox ESR 153.2, Firefox ESR 140.15, or Firefox 155 or later. Red Hat will provide updated Firefox packages through standard update channels. Until updates are applied, users should exercise caution when visiting untrusted websites.
Pac
Mozilla
Mozilla Foundation Security Advisory 2026-86: CVE-2026-84140
vendor_mozilla
CVE-2026-84140 Mozilla Foundation Security Advisory 2026-86: CVE-2026-84140
Mozilla Foundation Security Advisory 2026-86
CVE: CVE-2026-84140
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 155
Mozilla
Mozilla Foundation Security Advisory 2026-88: CVE-2026-84140
vendor_mozilla
CVE-2026-84140 Mozilla Foundation Security Advisory 2026-88: CVE-2026-84140
Mozilla Foundation Security Advisory 2026-88
CVE: CVE-2026-84140
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 153.2
Mozilla
Mozilla Foundation Security Advisory 2026-82: CVE-2026-84140
vendor_mozilla
CVE-2026-84140 Mozilla Foundation Security Advisory 2026-82: CVE-2026-84140
Mozilla Foundation Security Advisory 2026-82
CVE: CVE-2026-84140
Product: Firefox
Impact: high
Fixed in: Firefox 155
Mozilla
Mozilla Foundation Security Advisory 2026-85: CVE-2026-84140
vendor_mozilla
CVE-2026-84140 Mozilla Foundation Security Advisory 2026-85: CVE-2026-84140
Mozilla Foundation Security Advisory 2026-85
CVE: CVE-2026-84140
Product: Firefox ESR
Impact: high
Fixed in: Firefox ESR 153.2
VulDB
Mozilla Firefox up to 153.1/154 Navigation isolation (Nessus ID 342307)
vuldb·2026-09-03
CVE-2026-84140 [CRITICAL] Mozilla Firefox up to 153.1/154 Navigation isolation (Nessus ID 342307)
A vulnerability classified as critical was found in Mozilla Firefox up to 153.1/154. Affected by this vulnerability is an unknown functionality of the component Navigation Component. Such manipulation leads to improper isolation or compartmentalization.
This vulnerability is listed as CVE-2026-84140. The attack may be performed from remote. There is no available exploit.
Upgrading the affected component is advised.
GHSA
Site isolation issue in the DOM: Navigation component.
ghsa_unreviewed·2026-09-01
CVE-2026-84140 Site isolation issue in the DOM: Navigation component.
Site isolation issue in the DOM: Navigation component. This vulnerability was fixed in Firefox 155 and Firefox ESR 153.2.
No detection rules found.
No public exploits indexed.
2026-09-01
Published