CVE-2026-16387
CRITICALCVSS 9.8/10EPSS 0.22%
Last modified
CVE-2026-16387 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. Site isolation issue in the Networking component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.. EPSS estimates a 0.22% chance of exploitation in the next 30 days.
Description
Site isolation issue in the Networking component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Firefox | < 140.13.0 |
| Mozilla | Firefox | < 153.0.0 |
| Mozilla | Thunderbird | < 140.13.0 |
| Mozilla | Thunderbird | >= 141.0, < 153.0 |
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=2043200Permissions Required
- https://www.mozilla.org/security/advisories/mfsa2026-68/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-70/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-71/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-72/Vendor Advisory
Timeline
- Published
- Last Modified
- Status
- Analyzed
Frequently Asked Questions
What is 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.
How severe is CVE-2026-16387?
CVE-2026-16387 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 0.22% probability of exploitation in the next 30 days.
How do I fix CVE-2026-16387?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.
How Strix Helps
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Are you affected by CVE-2026-16387?
Run a free Strix scan to check your systems for this vulnerability.
Scan your code nowSource: NVD / NIST