CVE-2026-74989
Critical
Description
Internally found bugs present in Thunderbird 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 154 and Thunderbird 154.
SeverityCritical
CVSS9.8
Exploit probability—
Product
Mozilla Firefox
PublishedAug 18, 2026
First seenAug 18, 2026
Weakness typeCWE-119Memory buffer bounds error
How to fix
Update
- mozilla firefox154.0.0 or later
- mozilla thunderbird154.0 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mozilla firefox | v < 154.0.0 | 154.0.0 |
| mozilla thunderbird | v < 154.0 | 154.0 |
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