CVE-2026-12291
High
Description
Use-after-free in the Networking: HTTP component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.
SeverityHigh
CVSS8.8
Exploit probability—
Product
Mozilla Firefox
PublishedJun 16, 2026
First seenJun 16, 2026
Weakness typeCWE-416Use after freeCWE-825CWE-825
How to fix
Update
- mozilla firefox115.37.0, 152.0.0, 140.12.0 or later
- mozilla thunderbird140.12.0, 152.0.0 or later
Vendor advisories
- access.redhat.com/errata/RHSA-2026:38506
- access.redhat.com/errata/RHSA-2026:36100
- access.redhat.com/errata/RHSA-2026:38751
- access.redhat.com/errata/RHSA-2026:27733
- access.redhat.com/errata/RHSA-2026:30846
- access.redhat.com/errata/RHSA-2026:27717
- access.redhat.com/errata/RHSA-2026:33445
- access.redhat.com/errata/RHSA-2026:36102
- access.redhat.com/errata/RHSA-2026:39428
- access.redhat.com/errata/RHSA-2026:37210
- access.redhat.com/errata/RHSA-2026:39141
- access.redhat.com/errata/RHSA-2026:36103
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mozilla firefox | v < 115.37.0, v < 152.0.0, 128.0 ≤ v < 140.12.0 | 115.37.0, 152.0.0, 140.12.0 |
| mozilla thunderbird | v < 140.12.0, v < 152.0.0 | 140.12.0, 152.0.0 |
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.