Use-after-free in Mozilla products - CVE-2026-6759

Vulnerability identifier: #VU126667

CSH Severity: Low

CVSS v4: 6.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-6759

CWE-ID: CWE-416

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local user to cause a denial of service.

The vulnerability exists due to use-after-free in the Widget: Cocoa component when handling local widget operations. A local user can trigger the vulnerable code path to cause a denial of service.

Firefox for Android
Mozilla Firefox
Firefox ESR
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 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 High Performance Computing 12
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise Server for SAP Applications 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 Power, little endian - Extended Update Support
Red Hat Enterprise Linux for ARM 64 - Extended Update Support
Red Hat Enterprise Linux for IBM z Systems - Extended Update Support
Red Hat Enterprise Linux for x86_64 - 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-debugsource
firefox-debuginfo
firefox
thunderbird-wayland
thunderbird-librnp-rnp
thunderbird-debugsource
thunderbird-debuginfo
thunderbird
thunderbird (Red Hat package)
firefox (Red Hat package)
MozillaFirefox-devel
MozillaFirefox-debuginfo
MozillaFirefox
MozillaFirefox-translations-common
MozillaFirefox-debugsource
MozillaFirefox-translations-other
MozillaThunderbird-translations-other
MozillaThunderbird-debuginfo
MozillaThunderbird-translations-common
MozillaThunderbird
MozillaThunderbird-debugsource
Mozilla Thunderbird

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-debugsource - update to 140.10.0-1
firefox-debuginfo - update to 140.10.0-1
firefox - update to 140.10.0-1
thunderbird-wayland - update to 140.10.0-1
thunderbird-librnp-rnp - update to 140.10.0-1
thunderbird-debugsource - update to 140.10.0-1
thunderbird-debuginfo - update to 140.10.0-1
thunderbird - update to 140.10.0-1
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
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
firefox - update to 140.10.0-1.0.1
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-translations-other - update to 140.10.1-150200.8.271.1
MozillaThunderbird-debuginfo - update to 140.10.1-150200.8.271.1
MozillaThunderbird-translations-common - update to 140.10.1-150200.8.271.1
MozillaThunderbird - update to 140.10.1-150200.8.271.1
MozillaThunderbird-debugsource - update to 140.10.1-150200.8.271.1
thunderbird - update to 140.12.0-1.0.1

• https://www.mozilla.org/en-US/security/advisories/mfsa2026-32/
• https://www.mozilla.org/en-US/security/advisories/mfsa2026-30/
• https://bugzilla.mozilla.org/show_bug.cgi?id=2016164

• Multiple vulnerabilities in Mozilla Firefox
• Multiple vulnerabilities in Mozilla Thunderbird ESR
• Multiple vulnerabilities in Mozilla Thunderbird
• openEuler 24.03 LTS SP3 update for thunderbird
• openEuler 24.03 LTS SP3 update for firefox
• openEuler 24.03 LTS SP1 update for firefox
• openEuler 24.03 LTS update for firefox
• openEuler 22.03 LTS SP4 update for firefox
• Red Hat Enterprise Linux 9 update for firefox
• Red Hat Enterprise Linux 8 update for firefox
• Red Hat Enterprise Linux 10 update for firefox
• SUSE update for MozillaFirefox
• SUSE update for MozillaFirefox
• Red Hat Enterprise Linux 10 update for thunderbird
• Red Hat Enterprise Linux 8 update for thunderbird
• SUSE update for MozillaThunderbird
• Anolis OS update for firefox
• Red Hat Enterprise Linux 9 update for thunderbird
• Red Hat Enterprise Linux 8 update for firefox
• Red Hat Enterprise Linux 9 update for firefox
• Red Hat Enterprise Linux 9 update for firefox
• Red Hat Enterprise Linux 10 update for firefox
• Red Hat Enterprise Linux 9 update for thunderbird
• Red Hat Enterprise Linux 9 update for thunderbird
• Red Hat Enterprise Linux 8 update for thunderbird
• Red Hat Enterprise Linux 8 update for thunderbird
• Red Hat Enterprise Linux 8 update for firefox
• Red Hat Enterprise Linux 8 update for firefox
• Red Hat Enterprise Linux 7 Extended Lifecycle Support update for firefox
• Anolis OS update for thunderbird