CVE-2026-84120
Medium
Description
Use-after-free in the Audio/Video component. This vulnerability was fixed in Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.
SeverityMedium
CVSS5.4
Exploit probability—
Product
Mozilla Firefox
PublishedSep 1, 2026
First seenSep 1, 2026
Weakness typeCWE-416Use after free
How to fix
Update
- mozilla firefox115.40.0, 140.15.0, 153.2.0, 155.0.0 or later
- mozilla thunderbird140.15.0, 153.2.0, 155.0 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mozilla firefox | v < 115.40.0, 116.0 ≤ v < 140.15.0, 141.0.0 ≤ v < 153.2.0, 154.0.0 ≤ v < 155.0.0 | 115.40.0, 140.15.0, 153.2.0, 155.0.0 |
| mozilla thunderbird | v < 140.15.0, 141.0 ≤ v < 153.2.0, 154.0 ≤ v < 155.0 | 140.15.0, 153.2.0, 155.0 |
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