CVE-2026-4692
Critical
Description
Sandbox escape in the Responsive Design Mode component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
SeverityCritical
CVSS10.0
Exploit probability—
Product
Mozilla Firefox
PublishedMar 24, 2026
First seenMar 24, 2026
Weakness typeCWE-653CWE-653
How to fix
Update
- mozilla firefox115.34.0, 149.0, 140.9.0 or later
- mozilla thunderbird140.9.0, 149.0 or later
Vendor advisories
- access.redhat.com/errata/RHSA-2026:8427
- access.redhat.com/errata/RHSA-2026:7843
- access.redhat.com/errata/RHSA-2026:8315
- access.redhat.com/errata/RHSA-2026:5931
- access.redhat.com/errata/RHSA-2026:6342
- access.redhat.com/errata/RHSA-2026:5932
- access.redhat.com/errata/RHSA-2026:6917
- access.redhat.com/errata/RHSA-2026:7840
- access.redhat.com/errata/RHSA-2026:8285
- access.redhat.com/errata/RHSA-2026:7858
- access.redhat.com/errata/RHSA-2026:8850
- access.redhat.com/errata/RHSA-2026:7842
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mozilla firefox | v < 115.34.0, v < 149.0, 128.0 ≤ v < 140.9.0 | 115.34.0, 149.0, 140.9.0 |
| mozilla thunderbird | v < 140.9.0, v < 149.0 | 140.9.0, 149.0 |
Check your version
Choose the product and enter the version you run to see whether it falls in the affected range.
In the Intelligence 360 plan
Attack Surface Management
See the assets tied to your domains, the technologies they run and known vulnerabilities in one list.