CVE-2026-4689
Critical
Description
Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
SeverityCritical
CVSS10.0
Exploit probability—
Product
Mozilla Firefox
PublishedMar 24, 2026
First seenMar 24, 2026
Weakness typeCWE-120CWE-120CWE-190Integer overflow
How to fix
Update
- mozilla firefox115.34.0, 149.0, 140.9.0 or later
- mozilla thunderbird140.9.0, 149.0 or later
Vendor advisories
- access.redhat.com/errata/RHSA-2026:8427
- access.redhat.com/errata/RHSA-2026:7843
- access.redhat.com/errata/RHSA-2026:8315
- access.redhat.com/errata/RHSA-2026:5931
- access.redhat.com/errata/RHSA-2026:6342
- access.redhat.com/errata/RHSA-2026:5932
- access.redhat.com/errata/RHSA-2026:6917
- access.redhat.com/errata/RHSA-2026:7840
- access.redhat.com/errata/RHSA-2026:8285
- access.redhat.com/errata/RHSA-2026:7858
- access.redhat.com/errata/RHSA-2026:8850
- access.redhat.com/errata/RHSA-2026:7842
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mozilla firefox | v < 115.34.0, v < 149.0, 128.0 ≤ v < 140.9.0 | 115.34.0, 149.0, 140.9.0 |
| mozilla thunderbird | v < 140.9.0, v < 149.0 | 140.9.0, 149.0 |
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