CVE-2026-12304
CRITICALCVSS 9.1/10EPSS 0.19%
Last modified
CVE-2026-12304 is a critical-severity vulnerability rated 9.1/10 on the CVSS scale. Same-origin policy bypass in the Networking: Cookies component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12.. EPSS estimates a 0.19% chance of exploitation in the next 30 days.
Description
Same-origin policy bypass in the Networking: Cookies component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12.
Metrics
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Firefox | < 140.12.0 |
| Mozilla | Firefox | < 152.0.0 |
| Mozilla | Thunderbird | < 140.12.0 |
| Mozilla | Thunderbird | < 152.0.0 |
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=2034944Permissions Required
- https://www.mozilla.org/security/advisories/mfsa2026-57/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-58/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-60/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-61/Vendor Advisory
Timeline
- Published
- Last Modified
- Status
- Analyzed
Frequently Asked Questions
What is CVE-2026-12304?
Same-origin policy bypass in the Networking: Cookies component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12.
How severe is CVE-2026-12304?
CVE-2026-12304 has a CVSS score of 9.1/10 (CRITICAL severity). The EPSS model estimates a 0.19% probability of exploitation in the next 30 days.
How do I fix CVE-2026-12304?
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.
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Are you affected by CVE-2026-12304?
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