CVE-2026-16387

Site isolation issue in the Networking component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.

CVSS 3.1

9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS

0.3% chance of exploitation in the next 30 days; higher than 20% of CVEs (scores of 2026-10-25)

CWEs

CWE-200, CWE-284, CWE-346

Published

2026-07-21

Modified

2026-10-24

Record from

the NVD, synced 2026-10-25

Affected

• mozilla:firefox
• mozilla:thunderbird

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=2043200
• https://www.mozilla.org/security/advisories/mfsa2026-68/
• https://www.mozilla.org/security/advisories/mfsa2026-70/
• https://www.mozilla.org/security/advisories/mfsa2026-71/
• https://www.mozilla.org/security/advisories/mfsa2026-72/

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