CVE-2026-100816 Mozilla Firefox - Site Isolation Bypass

Mozilla Firefox contains a site isolation issue in the DOM Networking component, letting attackers bypass site isolation protections, exploit requires unspecified conditions.

CVSS base score 8.1 /10
High
CISA KEV
Not listed
Public exploit
None known
EPSS
0.15% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Site Isolation Bypass
Impact
Information Disclosure
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
Published
29 September 2026
Updated
15 October 2026
Weakness
CWE-346

Vendor fix

Update to Firefox ESR 153.4, Firefox 157 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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