Integer overflow in Firefox ESR - CVE-2026-8949

Vulnerability identifier: #VU131837

CSH Severity: Low

CVSS v4: 8.5 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-8949

CWE-ID: CWE-190

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local user to execute arbitrary code.

The vulnerability exists due to integer overflow in the Widget: Win32 component when handling local interaction with the application. A local user can trigger the integer overflow to execute arbitrary code.

The issue affects the Win32-specific component.

Firefox ESR
Mozilla Firefox
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 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 for SAP Applications 15
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise Server for SAP Applications 12
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Workstation Extension 15
Desktop Applications Module
SUSE Package Hub 15
openEuler
Mozilla Thunderbird
Firefox for Android
firefox-debuginfo
firefox-debugsource
firefox
MozillaFirefox-devel
MozillaFirefox
MozillaFirefox-debugsource
MozillaFirefox-debuginfo
MozillaFirefox-translations-common
MozillaThunderbird-translations-other
MozillaThunderbird-translations-common
MozillaThunderbird-debuginfo
MozillaThunderbird
MozillaThunderbird-debugsource
MozillaFirefox-translations-other
thunderbird-librnp-rnp
thunderbird-wayland
thunderbird-debugsource
thunderbird-debuginfo
thunderbird

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-debuginfo - update to 140.11.0-1
firefox-debugsource - update to 140.11.0-1
firefox - update to 140.11.0-1
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-debugsource - 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-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
MozillaThunderbird-debugsource - 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-debugsource - update to 140.12.0-1
thunderbird-debuginfo - update to 140.12.0-1
thunderbird - update to 140.12.0-1

• https://www.mozilla.org/en-US/security/advisories/mfsa2026-48/
• https://bugzilla.mozilla.org/show_bug.cgi?id=1355639

• Multiple vulnerabilities in Mozilla Firefox ESR 140
• Multiple vulnerabilities in Mozilla Firefox
• SUSE update for MozillaFirefox
• Multiple vulnerabilities in Thunderbird ESR
• Multiple vulnerabilities in Mozilla Thunderbird
• openEuler 24.03 LTS update for firefox
• openEuler 22.03 LTS SP4 update for firefox
• openEuler 24.03 LTS SP3 update for firefox
• SUSE update for MozillaFirefox
• openEuler 24.03 LTS SP1 update for firefox
• SUSE update for MozillaThunderbird
• openEuler 24.03 LTS SP3 update for thunderbird