Out-of-bounds write in Firefox ESR and Mozilla Firefox - CVE-2025-4918,CVE-2025-4920

Vulnerability identifier: #VU109400

CSH Severity: High

CVSS v4.0: 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/E:U/U:Amber

CVE-ID: CVE-2025-4918,CVE-2025-4920

CWE-ID: CWE-787

Exploitation vector: Remote access

Exploit availability: No public exploit available

Affected software:
Firefox ESR
Mozilla Firefox
Debian Linux
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server 15 SP3
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 Server 12
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise Workstation Extension 15
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Desktop 15
Anolis OS
SUSE Enterprise Storage
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for x86_64
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 Power, little endian - Extended Update Support
Red Hat Enterprise Linux for ARM 64 - Extended Update Support
Red Hat Enterprise Linux for x86_64 - Extended Update Support
Red Hat Enterprise Linux for IBM z Systems - Extended Update Support
Slackware Linux
SUSE Package Hub 15
Desktop Applications Module
openSUSE Leap
openEuler
Ubuntu
Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions
mozilla-firefox
firefox-esr (Debian package)
firefox-debuginfo
firefox-debugsource
firefox
firefox (Red Hat package)
MozillaFirefox-translations-common
MozillaFirefox
MozillaFirefox-devel
MozillaFirefox-debugsource
MozillaFirefox-debuginfo
MozillaFirefox-branding-upstream
MozillaFirefox-translations-other
MozillaThunderbird-debuginfo
MozillaThunderbird-translations-common
MozillaThunderbird-translations-other
MozillaThunderbird-debugsource
MozillaThunderbird
thunderbird (Debian package)
thunderbird (Red Hat package)
thunderbird
thunderbird-debuginfo
thunderbird-debugsource
thunderbird-librnp-rnp
thunderbird-wayland
thunderbird (Ubuntu package)
Mozilla Thunderbird

The vulnerability allows a remote attacker to compromise vulnerable system.

The vulnerability exists due to a boundary error when processing JavaScript "Promise" object. A remote attacker can trick the victim into visiting a specially crafted website, trigger an out-of-bounds write and execute arbitrary code on the target system.

Install updates from vendor's website.

• https://bugzilla.mozilla.org/show_bug.cgi?id=1966612
• https://www.mozilla.org/security/advisories/mfsa2025-36/
• https://www.mozilla.org/security/advisories/mfsa2025-37/
• https://www.mozilla.org/en-US/security/advisories/mfsa2025-38/