CVE-2026-4700
Critical · CVSS 9.8Mozilla Firefox / Thunderbird — Authentication bypass via HTTP request smuggling / mitigation bypass (CWE-288, CWE-444)
- CVSS
- 9.8
- nvd
- EPSS
- —
- KEV
- No
- Class
- other
- NVD-CWE-noinfo, CWE-288, CWE-444
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.
Search profile — drives PoC discovery
Symbols Networking::HTTPnsHttpHandlernsHttpChannelmfsa2026-20mfsa2026-22mfsa2026-23mfsa2026-24bug2003766
Keywords CVE-2026-4700Firefox HTTP mitigation bypassFirefox 149 authentication bypassCWE-288 FirefoxCWE-444 HTTP request smuggling FirefoxThunderbird HTTP bypassmfsa2026-20bugzilla 2003766Firefox ESR 140.9 bypass
Versions: Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, Thunderbird < 140.9
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=2003766
- https://www.mozilla.org/security/advisories/mfsa2026-20/
- https://www.mozilla.org/security/advisories/mfsa2026-22/
- https://www.mozilla.org/security/advisories/mfsa2026-23/
- https://www.mozilla.org/security/advisories/mfsa2026-24/
- https://access.redhat.com/errata/RHSA-2026:5930
- https://access.redhat.com/errata/RHSA-2026:5931
- https://access.redhat.com/errata/RHSA-2026:5932
- https://access.redhat.com/errata/RHSA-2026:6188
- https://access.redhat.com/errata/RHSA-2026:6342
- https://access.redhat.com/errata/RHSA-2026:6917
- https://access.redhat.com/errata/RHSA-2026:7837
Status: enriched · ingested 2026-06-30T06:00:22.000Z · profiled 2026-07-01T12:30:14.000Z