CVE-2026-74960
published 2026-08-18CVE-2026-74960: Site isolation issue in the WebExtensions component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154…
PriorityP340high8.1CVSS 3.1
AVNACLPRNUIRSUCHIHAN
EPSS
0.16%
5.9th percentile
Site isolation issue in the WebExtensions component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.
Affected
14 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| mozilla | firefox | < Firefox 154 | Firefox 154 |
| mozilla | firefox | < 140.14.0 | 140.14.0 |
| mozilla | firefox | — | — |
| mozilla | firefox | >= 141.0 < 153.1.0 | 153.1.0 |
| mozilla | firefox_esr | < Firefox ESR 153.1 | Firefox ESR 153.1 |
| mozilla | firefox_esr | < Firefox ESR 140.14 | Firefox ESR 140.14 |
| mozilla | thunderbird | < Thunderbird 140.14 | Thunderbird 140.14 |
| mozilla | thunderbird | < Thunderbird 154 | Thunderbird 154 |
| mozilla | thunderbird | < Thunderbird 153.1 | Thunderbird 153.1 |
| mozilla | thunderbird | < 140.14.0 | 140.14.0 |
| mozilla | thunderbird | — | — |
| mozilla | thunderbird | >= 141.0 < 153.1.0 | 153.1.0 |
| rhel10 | firefox-flatpak | — | — |
| rhel10 | thunderbird-flatpak | — | — |
CVSS provenance
nvdv3.18.1HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
vendor_redhat6.1MEDIUM
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Red Hat
firefox: thunderbird: Site isolation issue in the WebExtensions component
vendor_redhat·2026-08-18·CVSS 6.1
CVE-2026-74960 [MEDIUM] CWE-501 firefox: thunderbird: Site isolation issue in the WebExtensions component
firefox: thunderbird: Site isolation issue in the WebExtensions component
A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue:
Site isolation issue in the WebExtensions 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) - Affected
Package: rhel10/firefox-flatpak (Red Hat Enterprise Linux 10) - Affected
Package: rhel10/thunderbird-flatpak (Red Hat Enterprise Linux 10) - Affected
Package: thunderbird (Red Hat Enterprise Linux 10) - Affected
Package: firefox (Red Hat Enterprise Linux 6) - Out of support scope
Package: thunderbird (Red Hat Enterprise Linux 6) - Out of support scope
Package
Mozilla
Mozilla Foundation Security Advisory 2026-74: CVE-2026-74960
vendor_mozilla
CVE-2026-74960 Mozilla Foundation Security Advisory 2026-74: CVE-2026-74960
Mozilla Foundation Security Advisory 2026-74
CVE: CVE-2026-74960
Product: Firefox
Impact: high
Fixed in: Firefox 154
Mozilla
Mozilla Foundation Security Advisory 2026-79: CVE-2026-74960
vendor_mozilla
CVE-2026-74960 Mozilla Foundation Security Advisory 2026-79: CVE-2026-74960
Mozilla Foundation Security Advisory 2026-79
CVE: CVE-2026-74960
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 140.14
Mozilla
Mozilla Foundation Security Advisory 2026-77: CVE-2026-74960
vendor_mozilla
CVE-2026-74960 Mozilla Foundation Security Advisory 2026-77: CVE-2026-74960
Mozilla Foundation Security Advisory 2026-77
CVE: CVE-2026-74960
Product: Firefox ESR
Impact: high
Fixed in: Firefox ESR 153.1
Mozilla
Mozilla Foundation Security Advisory 2026-78: CVE-2026-74960
vendor_mozilla
CVE-2026-74960 Mozilla Foundation Security Advisory 2026-78: CVE-2026-74960
Mozilla Foundation Security Advisory 2026-78
CVE: CVE-2026-74960
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 154
Mozilla
Mozilla Foundation Security Advisory 2026-76: CVE-2026-74960
vendor_mozilla
CVE-2026-74960 Mozilla Foundation Security Advisory 2026-76: CVE-2026-74960
Mozilla Foundation Security Advisory 2026-76
CVE: CVE-2026-74960
Product: Firefox ESR
Impact: high
Fixed in: Firefox ESR 140.14
Mozilla
Mozilla Foundation Security Advisory 2026-80: CVE-2026-74960
vendor_mozilla
CVE-2026-74960 Mozilla Foundation Security Advisory 2026-80: CVE-2026-74960
Mozilla Foundation Security Advisory 2026-80
CVE: CVE-2026-74960
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 153.1
GHSA
Site isolation issue in the WebExtensions component.
ghsa_unreviewed·2026-08-18
CVE-2026-74960 Site isolation issue in the WebExtensions component.
Site isolation issue in the WebExtensions component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, and Firefox ESR 153.1.
No detection rules found.
No public exploits indexed.
https://bugzilla.mozilla.org/show_bug.cgi?id=2049148https://www.mozilla.org/security/advisories/mfsa2026-74/https://www.mozilla.org/security/advisories/mfsa2026-76/https://www.mozilla.org/security/advisories/mfsa2026-77/https://www.mozilla.org/security/advisories/mfsa2026-78/https://www.mozilla.org/security/advisories/mfsa2026-79/https://www.mozilla.org/security/advisories/mfsa2026-80/
2026-08-18
Published