Protection Mechanism Failure in Mozilla products - CVE-2026-6771

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Main Vulnerability Database Vulnerabilities #VU126675

Protection Mechanism Failure in Mozilla products - CVE-2026-6771

Published: April 21, 2026


Vulnerability identifier: #VU126675
CSH Severity: Medium
CVSS v4: 5.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-6771
CWE-ID: CWE-693
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote attacker to bypass a security restriction.

The vulnerability exists due to improper restriction enforcement in the DOM: Security component when processing crafted web content. A remote attacker can trigger the vulnerable behavior to bypass a security restriction.

User interaction is required to visit a specially crafted website or URL.


Affected software

Firefox for Android
Mozilla Firefox
Firefox ESR
Debian Linux
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise Server for SAP Applications 12
SUSE Linux Enterprise Workstation Extension 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Real Time 15
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for ARM 64
Anolis OS
Red Hat Enterprise Linux Server - AUS
Red Hat Enterprise Linux Server - TUS
Red Hat Enterprise Linux for x86_64 - Extended Update Support
Red Hat Enterprise Linux for IBM z Systems - Extended Update Support
Red Hat Enterprise Linux for Power, little endian - Extended Update Support
Red Hat Enterprise Linux for ARM 64 - Extended Update Support
Desktop Applications Module
SUSE Package Hub 15
openEuler
Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions
firefox-esr (Debian package)
thunderbird (Debian package)
firefox-debugsource
firefox
firefox-debuginfo
thunderbird
thunderbird-debuginfo
thunderbird-debugsource
thunderbird-librnp-rnp
thunderbird-wayland
firefox (Red Hat package)
thunderbird (Red Hat package)
MozillaFirefox-devel
MozillaFirefox-debuginfo
MozillaFirefox
MozillaFirefox-translations-common
MozillaFirefox-debugsource
MozillaFirefox-translations-other
MozillaThunderbird
MozillaThunderbird-debuginfo
MozillaThunderbird-debugsource
MozillaThunderbird-translations-other
MozillaThunderbird-translations-common
Mozilla Thunderbird

How to mitigate CVE-2026-6771

Install security update from vendor's website.

Firefox for Android - update to 150.0
Mozilla Firefox - update to 150.0
Firefox ESR - update to 140.10.0
Mozilla Thunderbird - addressed in versions 140.10.0, 150.0
firefox-esr (Debian package) - addressed in versions 140.10.0esr-1~deb12u1, 140.10.0esr-1~deb13u1
thunderbird (Debian package) - addressed in versions 1:140.10.0esr-1~deb12u1, 1:140.10.0esr-1~deb13u1
firefox-debugsource - update to 140.10.0-1
firefox - addressed in versions 140.10.0-1, 140.10.0-1.0.1
firefox-debuginfo - update to 140.10.0-1
firefox - update to 140.10.0-1
thunderbird - update to 140.10.0-1
thunderbird-debuginfo - update to 140.10.0-1
thunderbird-debugsource - update to 140.10.0-1
thunderbird-librnp-rnp - update to 140.10.0-1
thunderbird-wayland - update to 140.10.0-1
firefox (Red Hat package) - addressed in versions 140.10.0-1.el8_4, 140.10.0-1.el8_6, 140.10.0-1.el8_8, 140.10.0-1.el8_10, 140.10.0-1.el9_0, 140.10.0-1.el9_2, 140.10.0-1.el9_7, 140.10.0-1.el10_0, 140.10.0-1.el10_1, 140.10.0-2.el7_9
thunderbird (Red Hat package) - addressed in versions 140.10.0-1.el8_4, 140.10.0-1.el8_8, 140.10.0-1.el8_10, 140.10.0-1.el9_2, 140.10.0-1.el9_6, 140.10.0-1.el9_7, 140.10.0-1.el10_1
MozillaFirefox-devel - addressed in versions 140.10.0-112.310.1, 140.10.0-150200.152.231.1
MozillaFirefox-debuginfo - addressed in versions 140.10.0-112.310.1, 140.10.0-150200.152.231.1
MozillaFirefox - addressed in versions 140.10.0-112.310.1, 140.10.0-150200.152.231.1
MozillaFirefox-translations-common - addressed in versions 140.10.0-112.310.1, 140.10.0-150200.152.231.1
MozillaFirefox-debugsource - addressed in versions 140.10.0-112.310.1, 140.10.0-150200.152.231.1
MozillaFirefox-translations-other - update to 140.10.0-150200.152.231.1
MozillaThunderbird - update to 140.10.1-150200.8.271.1
MozillaThunderbird-debuginfo - update to 140.10.1-150200.8.271.1
MozillaThunderbird-debugsource - update to 140.10.1-150200.8.271.1
MozillaThunderbird-translations-other - update to 140.10.1-150200.8.271.1
MozillaThunderbird-translations-common - update to 140.10.1-150200.8.271.1
thunderbird - update to 140.12.0-1.0.1

External References

Related Security Bulletins