Input validation error in Mozilla Firefox and Firefox for Android - CVE-2026-8391

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Main Vulnerability Database Vulnerabilities #VU131171

Input validation error in Mozilla Firefox and Firefox for Android - CVE-2026-8391

Published: May 12, 2026


Vulnerability identifier: #VU131171
CSH Severity: High
CVSS v4: 8.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-8391
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote attacker to compromise the affected system.

The vulnerability exists due to an unspecified issue in the JavaScript Engine component. A remote attacker can trick the victim into visiting a specially crafted website and execute arbitrary code on the system.


Affected software

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

How to mitigate CVE-2026-8391

Install updates from vendor's website.

Mozilla Firefox - update to 150.0.3
Firefox for Android - update to 150.0.3
Mozilla Thunderbird - update to 140.11.0
Firefox ESR - addressed in versions 115.36.0, 140.11.0
firefox-esr (Debian package) - addressed in versions 140.11.0esr-1~deb12u1, 140.11.0esr-1~deb13u1
thunderbird (Debian package) - addressed in versions 1:140.11.0esr-1~deb12u1, 1:140.11.0esr-1~deb13u1
firefox - update to 140.11.0-1
firefox-debugsource - update to 140.11.0-1
firefox-debuginfo - update to 140.11.0-1
firefox - addressed in versions 140.11.0-1, 140.11.0-1.0.1
firefox (Red Hat package) - addressed in versions 140.11.0-1.el7_9, 140.11.0-1.el8_4, 140.11.0-1.el8_6, 140.11.0-1.el8_8, 140.11.0-1.el8_10, 140.11.0-1.el9_2, 140.11.0-1.el9_4, 140.11.0-1.el9_6, 140.11.0-1.el9_8, 140.11.0-1.el10_0, 140.11.0-1.el10_2
thunderbird (Red Hat package) - addressed in versions 140.11.0-1.el8_4, 140.11.0-1.el8_6, 140.11.0-1.el8_8, 140.11.0-1.el8_10, 140.11.0-1.el9_2, 140.11.0-1.el9_4, 140.11.0-1.el9_6, 140.11.0-1.el9_8, 140.11.0-1.el10_0, 140.11.0-1.el10_2
MozillaFirefox-debugsource - addressed in versions 140.11.0-112.318.1, 140.11.0-150200.152.239.1
MozillaFirefox-devel - addressed in versions 140.11.0-112.318.1, 140.11.0-150200.152.239.1
MozillaFirefox - addressed in versions 140.11.0-112.318.1, 140.11.0-150200.152.239.1
MozillaFirefox-debuginfo - addressed in versions 140.11.0-112.318.1, 140.11.0-150200.152.239.1
MozillaFirefox-translations-common - addressed in versions 140.11.0-112.318.1, 140.11.0-150200.152.239.1
MozillaThunderbird-debuginfo - update to 140.11.0-150200.8.274.1
MozillaThunderbird-translations-other - update to 140.11.0-150200.8.274.1
MozillaThunderbird-translations-common - update to 140.11.0-150200.8.274.1
MozillaThunderbird - update to 140.11.0-150200.8.274.1
MozillaThunderbird-debugsource - update to 140.11.0-150200.8.274.1
MozillaFirefox-translations-other - update to 140.11.0-150200.152.239.1
thunderbird - update to 140.12.0-1
thunderbird-debuginfo - update to 140.12.0-1
thunderbird-debugsource - update to 140.12.0-1
thunderbird-librnp-rnp - update to 140.12.0-1
thunderbird-wayland - update to 140.12.0-1
thunderbird - update to 140.12.0-1.0.1

External References

Related Security Bulletins