CVE-2026-5735
Critical
Description
Memory safety bugs present in Firefox 149.0.1 and Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 149.0.2 and Thunderbird 149.0.2.
SeverityCritical
CVSS9.8
Exploit probability—
Product
Mozilla Firefox
PublishedApr 7, 2026
First seenApr 7, 2026
Weakness typeCWE-125Out-of-bounds readCWE-787Out-of-bounds write
How to fix
Update
- mozilla firefox149.0.2 or later
- mozilla thunderbird149.0.2 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mozilla firefox | v < 149.0.2 | 149.0.2 |
| mozilla thunderbird | v < 149.0.2 | 149.0.2 |
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