Input validation error in Firefox ESR - CVE-2026-7321

Vulnerability identifier: #VU128409

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:L/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-7321

CWE-ID: CWE-20

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to escape the sandbox.

The vulnerability exists due to incorrect boundary conditions in the WebRTC: Networking component when handling WebRTC network traffic. A remote attacker can trigger specially crafted WebRTC network interactions to escape the sandbox.

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

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

Install security update from vendor's website.

Firefox ESR - update to 140.10.1
thunderbird (Debian package) - addressed in versions 1:140.10.1esr-1~deb12u1, 1:140.10.1esr-1~deb13u1
firefox-esr (Debian package) - addressed in versions 140.10.1esr-1~deb12u1, 140.10.1esr-1~deb13u1
firefox-debuginfo - addressed in versions 140.10.1-1, 140.10.1-2
firefox - addressed in versions 140.10.1-1, 140.10.1-2
thunderbird-wayland - update to 140.10.1-1
thunderbird-librnp-rnp - update to 140.10.1-1
thunderbird-debugsource - update to 140.10.1-1
thunderbird-debuginfo - update to 140.10.1-1
thunderbird - update to 140.10.1-1
firefox-debugsource - addressed in versions 140.10.1-1, 140.10.1-2
firefox (Red Hat package) - addressed in versions 140.10.1-1.el7_9, 140.10.1-1.el8_6, 140.10.1-1.el8_8, 140.10.1-1.el8_10, 140.10.1-1.el9_0, 140.10.1-1.el9_2, 140.10.1-1.el9_4, 140.10.1-1.el9_6
thunderbird (Red Hat package) - addressed in versions 140.10.1-1.el8_4, 140.10.1-1.el8_6, 140.10.1-1.el8_10, 140.10.1-1.el9_4, 140.10.1-1.el9_6, 140.10.1-1.el10_0
firefox - update to 140.10.1-1.0.1
MozillaThunderbird-debuginfo - update to 140.10.1-150200.8.271.1
MozillaThunderbird-debugsource - update to 140.10.1-150200.8.271.1
MozillaThunderbird-translations-common - update to 140.10.1-150200.8.271.1
MozillaThunderbird - update to 140.10.1-150200.8.271.1
MozillaThunderbird-translations-other - update to 140.10.1-150200.8.271.1
MozillaFirefox-translations-common - addressed in versions 140.10.1-150200.152.234.1, 140.10.2-112.313.1
MozillaFirefox-devel - addressed in versions 140.10.1-150200.152.234.1, 140.10.2-112.313.1
MozillaFirefox-debuginfo - addressed in versions 140.10.1-150200.152.234.1, 140.10.2-112.313.1
MozillaFirefox-translations-other - update to 140.10.1-150200.152.234.1
MozillaFirefox - addressed in versions 140.10.1-150200.152.234.1, 140.10.2-112.313.1
MozillaFirefox-debugsource - addressed in versions 140.10.1-150200.152.234.1, 140.10.2-112.313.1
thunderbird - update to 140.12.0-1.0.1

• https://www.mozilla.org/en-US/security/advisories/mfsa2026-36/
• https://bugzilla.mozilla.org/show_bug.cgi?id=2029461

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