Improper access control in Firefox ESR - CVE-2026-8950

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Main Vulnerability Database Vulnerabilities #VU131838

Improper access control in Firefox ESR - CVE-2026-8950

Published: May 19, 2026


Vulnerability identifier: #VU131838
CSH Severity: High
CVSS v4: 7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-8950
CWE-ID: CWE-284
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote attacker to bypass the same-origin policy.

The vulnerability exists due to improper access control in the Networking: HTTP component when handling crafted web content. A remote attacker can cause the browser to process crafted content to bypass the same-origin policy.

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


Affected software

Firefox ESR
Mozilla Firefox
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 15 SP6
Debian Linux
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise High Performance Computing ESPOS 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
Anolis OS
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
Red Hat Enterprise Linux Server - AUS
Red Hat Enterprise Linux Server - TUS
Red Hat Enterprise Linux for IBM z Systems - Extended Update Support
Red Hat Enterprise Linux for x86_64 - 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
firefox-debugsource
firefox-debuginfo
firefox (Red Hat package)
thunderbird (Red Hat package)
MozillaFirefox-translations-common
MozillaFirefox-debugsource
MozillaFirefox
MozillaFirefox-devel
MozillaFirefox-debuginfo
MozillaThunderbird-debugsource
MozillaThunderbird-translations-other
MozillaThunderbird-translations-common
MozillaThunderbird-debuginfo
MozillaThunderbird
MozillaFirefox-translations-other
thunderbird-librnp-rnp
thunderbird-wayland
thunderbird
thunderbird-debuginfo
thunderbird-debugsource
Mozilla Thunderbird
Firefox for Android

How to mitigate CVE-2026-8950

Install security update from vendor's website.

Firefox ESR - update to 140.11.0
Mozilla Thunderbird - addressed in versions 140.11.0, 151.0
Mozilla Firefox - update to 151.0
Firefox for Android - update to 151.0
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 - addressed in versions 140.11.0-1, 140.11.0-1.0.1
firefox-debugsource - update to 140.11.0-1
firefox-debuginfo - update to 140.11.0-1
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-translations-common - addressed in versions 140.11.0-112.318.1, 140.11.0-150200.152.239.1
MozillaFirefox-debugsource - 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-devel - 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
MozillaThunderbird-debugsource - 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-debuginfo - update to 140.11.0-150200.8.274.1
MozillaThunderbird - update to 140.11.0-150200.8.274.1
MozillaFirefox-translations-other - update to 140.11.0-150200.152.239.1
thunderbird-librnp-rnp - update to 140.12.0-1
thunderbird-wayland - update to 140.12.0-1
thunderbird - update to 140.12.0-1
thunderbird-debuginfo - update to 140.12.0-1
thunderbird-debugsource - update to 140.12.0-1
thunderbird - update to 140.12.0-1.0.1

External References

Related Security Bulletins