CVE-2026-74956
Critical
Description
Same-origin policy bypass in the DOM: Service Workers component. This vulnerability was fixed in Firefox 154, Firefox ESR 153.1, Thunderbird 154, and Thunderbird 153.1.
SeverityCritical
CVSS9.1
Exploit probability—
Product
Mozilla Firefox
PublishedAug 18, 2026
First seenAug 18, 2026
Weakness typeCWE-843CWE-843
How to fix
Update
- mozilla firefox153.1.0, 154.0.0 or later
- mozilla thunderbird153.1.0, 154.0 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mozilla firefox | v < 153.1.0, v < 154.0.0 | 153.1.0, 154.0.0 |
| mozilla thunderbird | v < 153.1.0, v < 154.0 | 153.1.0, 154.0 |
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