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Vulnerability · Published Mar 24, 2026 · Assigned by mozilla

CVE-2026-4700Mitigation bypass in the Networking: HTTP component

Critical 9.8

In plain English

A critical-severity authentication bypass in Firefox from Mozilla. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.9% (higher than 60% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)9.8Critical
Exploit odds (30 days)0.9%top 39.6% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
AlmaLinux:10firefox140.9.0-1.el10_1ALSA-2026:5931
AlmaLinux:8firefox140.9.0-1.el8_10.alma.1ALSA-2026:5932
AlmaLinux:9firefox140.9.0-1.el9_7.alma.1ALSA-2026:5930
AlmaLinux:9firefox-x11140.9.0-1.el9_7.alma.1ALSA-2026:5930
AlmaLinux:10thunderbird140.9.0-1.el10_1.alma.1ALSA-2026:6342
AlmaLinux:8thunderbird140.9.0-1.el8_10.alma.1ALSA-2026:6917
AlmaLinux:9thunderbird140.9.0-1.el9_7.alma.1ALSA-2026:6188
Debian:12firefox-esr140.9.0esr-1~deb12u1DSA-6178-1
Debian:12firefox-esr140.9.0esr-1~deb12u1DEBIAN-CVE-2026-4700
Debian:13firefox-esr140.9.0esr-1~deb13u1DEBIAN-CVE-2026-4700
Debian:13firefox-esr140.9.0esr-1~deb13u1DSA-6178-1
Debian:14firefox-esr140.9.0esr-1DEBIAN-CVE-2026-4700
Debian:12thunderbird1:140.9.0esr-1~deb12u1DSA-6179-1
Debian:12thunderbird1:140.9.0esr-1~deb12u1DEBIAN-CVE-2026-4700
Debian:13thunderbird1:140.9.0esr-1~deb13u1DEBIAN-CVE-2026-4700
Debian:13thunderbird1:140.9.0esr-1~deb13u1DSA-6179-1
Debian:14thunderbird1:140.9.0esr-1DEBIAN-CVE-2026-4700
Rocky Linux:10firefox0:140.9.0-1.el10_1RLSA-2026:5931
Rocky Linux:8firefox0:140.9.0-1.el8_10RLSA-2026:5932
Rocky Linux:9firefox0:140.9.0-1.el9_7RLSA-2026:5930
Rocky Linux:10thunderbird0:140.9.0-1.el10_1RLSA-2026:6342
Rocky Linux:8thunderbird0:140.9.0-1.el8_10RLSA-2026:6917
Rocky Linux:9thunderbird0:140.9.0-1.el9_7RLSA-2026:6188
Ubuntu:22.04:LTSmozjs102no fix listedUBUNTU-CVE-2026-4700
Ubuntu:24.04:LTSmozjs102no fix listedUBUNTU-CVE-2026-4700
Ubuntu:24.04:LTSmozjs115no fix listedUBUNTU-CVE-2026-4700
Ubuntu:22.04:LTSmozjs78no fix listedUBUNTU-CVE-2026-4700
Ubuntu:22.04:LTSmozjs91no fix listedUBUNTU-CVE-2026-4700
Ubuntu:22.04:LTSthunderbirdno fix listedUBUNTU-CVE-2026-4700

Affected products (as reported)

VendorProductVersions
Mozilla Firefox see references
Mozilla Thunderbird see references

Weakness: CWE-288, CWE-444 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References