CVE-2026-74986
published 2026-08-18CVE-2026-74986: Site isolation issue in the CSS Parsing and Computation component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and…
PriorityP349critical9.1CVSS 3.1
AVNACLPRNUINSUCHINAH
EPSS
0.32%
24.6th percentile
Site isolation issue in the CSS Parsing and Computation component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
Affected
6 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| mozilla | firefox | < Firefox 154 | Firefox 154 |
| mozilla | firefox | < 153.1.0 | 153.1.0 |
| mozilla | firefox_esr | < Firefox ESR 153.1 | Firefox ESR 153.1 |
| mozilla | thunderbird | < Thunderbird 153.1 | Thunderbird 153.1 |
| mozilla | thunderbird | < Thunderbird 154 | Thunderbird 154 |
| mozilla | thunderbird | < 153.1.0 | 153.1.0 |
CVSS provenance
nvdv3.19.1CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
vendor_redhat9.1CRITICAL
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GHSA
Site isolation issue in the CSS Parsing and Computation component.
ghsa_unreviewed·2026-08-18
CVE-2026-74986 Site isolation issue in the CSS Parsing and Computation component.
Site isolation issue in the CSS Parsing and Computation component. This vulnerability was fixed in Firefox 154 and Firefox ESR 153.1.
Red Hat
firefox: thunderbird: Site isolation issue in the CSS Parsing and Computation component
vendor_redhat·2026-08-18·CVSS 9.1
CVE-2026-74986 [CRITICAL] CWE-501 firefox: thunderbird: Site isolation issue in the CSS Parsing and Computation component
firefox: thunderbird: Site isolation issue in the CSS Parsing and Computation component
A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue:
Site isolation issue in the CSS Parsing and Computation component
Statement: Red Hat Product Security rates the severity of this flaw as determined by the Mozilla Foundation Security Advisory.
Package: firefox (Red Hat Enterprise Linux 10) - Not affected
Package: rhel10/firefox-flatpak (Red Hat Enterprise Linux 10) - Not affected
Package: rhel10/thunderbird-flatpak (Red Hat Enterprise Linux 10) - Not affected
Package: thunderbird (Red Hat Enterprise Linux 10) - Not affected
Package: firefox (Red Hat Enterprise Linux 6) - Not affected
Package: thunderbird (Red Hat Enterprise Linu
Mozilla
Mozilla Foundation Security Advisory 2026-77: CVE-2026-74986
vendor_mozilla
CVE-2026-74986 Mozilla Foundation Security Advisory 2026-77: CVE-2026-74986
Mozilla Foundation Security Advisory 2026-77
CVE: CVE-2026-74986
Product: Firefox ESR
Impact: high
Fixed in: Firefox ESR 153.1
Mozilla
Mozilla Foundation Security Advisory 2026-80: CVE-2026-74986
vendor_mozilla
CVE-2026-74986 Mozilla Foundation Security Advisory 2026-80: CVE-2026-74986
Mozilla Foundation Security Advisory 2026-80
CVE: CVE-2026-74986
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 153.1
Mozilla
Mozilla Foundation Security Advisory 2026-78: CVE-2026-74986
vendor_mozilla
CVE-2026-74986 Mozilla Foundation Security Advisory 2026-78: CVE-2026-74986
Mozilla Foundation Security Advisory 2026-78
CVE: CVE-2026-74986
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 154
Mozilla
Mozilla Foundation Security Advisory 2026-74: CVE-2026-74986
vendor_mozilla
CVE-2026-74986 Mozilla Foundation Security Advisory 2026-74: CVE-2026-74986
Mozilla Foundation Security Advisory 2026-74
CVE: CVE-2026-74986
Product: Firefox
Impact: high
Fixed in: Firefox 154
No detection rules found.
No public exploits indexed.
2026-08-18
Published