CVE-2026-16375
published 2026-07-21CVE-2026-16375: Site isolation issue in the Networking: HTTP component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird…
PriorityP351critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
EPSS
0.21%
11.2th percentile
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.
Affected
12 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| mozilla | firefox | < Firefox 153 | Firefox 153 |
| mozilla | firefox | < 140.13.0 | 140.13.0 |
| mozilla | firefox | < 153.0.0 | 153.0.0 |
| mozilla | firefox | — | — |
| mozilla | firefox_esr | < Firefox ESR 140.13 | Firefox ESR 140.13 |
| mozilla | thunderbird | < Thunderbird 140.13 | Thunderbird 140.13 |
| mozilla | thunderbird | < Thunderbird 153 | Thunderbird 153 |
| mozilla | thunderbird | < 140.13.0 | 140.13.0 |
| mozilla | thunderbird | — | — |
| mozilla | thunderbird | >= 141.0 < 153.0 | 153.0 |
| rhel10 | firefox-flatpak | — | — |
| rhel10 | thunderbird-flatpak | — | — |
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 Networking: HTTP component
vendor_redhat·2026-07-21·CVSS 9.8
CVE-2026-16375 [CRITICAL] firefox: thunderbird: Site isolation issue in the Networking: HTTP component
firefox: thunderbird: Site isolation issue in the Networking: HTTP component
A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue:
Site isolation issue in the Networking: HTTP 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
P
Mozilla
Mozilla Foundation Security Advisory 2026-68: CVE-2026-16375
vendor_mozilla
CVE-2026-16375 Mozilla Foundation Security Advisory 2026-68: CVE-2026-16375
Mozilla Foundation Security Advisory 2026-68
CVE: CVE-2026-16375
Product: Firefox
Impact: high
Fixed in: Firefox 153
Mozilla
Mozilla Foundation Security Advisory 2026-70: CVE-2026-16375
vendor_mozilla
CVE-2026-16375 Mozilla Foundation Security Advisory 2026-70: CVE-2026-16375
Mozilla Foundation Security Advisory 2026-70
CVE: CVE-2026-16375
Product: Firefox ESR
Impact: high
Fixed in: Firefox ESR 140.13
Mozilla
Mozilla Foundation Security Advisory 2026-72: CVE-2026-16375
vendor_mozilla
CVE-2026-16375 Mozilla Foundation Security Advisory 2026-72: CVE-2026-16375
Mozilla Foundation Security Advisory 2026-72
CVE: CVE-2026-16375
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 140.13
Mozilla
Mozilla Foundation Security Advisory 2026-71: CVE-2026-16375
vendor_mozilla
CVE-2026-16375 Mozilla Foundation Security Advisory 2026-71: CVE-2026-16375
Mozilla Foundation Security Advisory 2026-71
CVE: CVE-2026-16375
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 153
GHSA
Site isolation issue in the Networking: HTTP component.
ghsa_unreviewed·2026-07-21
CVE-2026-16375 [CRITICAL] CWE-346 Site isolation issue in the Networking: HTTP component.
Site isolation issue in the Networking: HTTP component. This vulnerability was fixed in Firefox 153 and Firefox ESR 140.13.
No detection rules found.
No public exploits indexed.
2026-07-21
Published