CVE-2026-4700
Critical
Description
Mitigation bypass in the Networking: HTTP component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
SeverityCritical
CVSS9.8
Exploit probability60. percentile0.9%
Product
Mozilla Firefox
PublishedMar 24, 2026
First seenMar 24, 2026
Weakness typeCWE-288CWE-288CWE-444CWE-444
How to fix
Update
- mozilla firefox140.9.0, 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 < 140.9.0, v < 149.0 | 140.9.0, 149.0 |
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