Use-after-free in Mozilla products - CVE-2026-12291

Vulnerability identifier: #VU134606

CSH Severity: High

CVSS v4.0: CVSS:4.0/AV:L/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-2026-12291

CWE-ID: CWE-416

Exploitation vector: Remote access

Exploit availability: No public exploit available

Affected software:
Mozilla Firefox
Firefox ESR
Firefox for Android
Debian Linux
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise Server for SAP Applications 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 Desktop 15
SUSE Linux Enterprise Workstation Extension 15
SUSE Linux Enterprise Real Time 15
Anolis OS
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 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
Red Hat Enterprise Linux for IBM z Systems
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-librnp-rnp
firefox-debugsource
firefox-debuginfo
firefox
thunderbird-wayland
thunderbird-debugsource
thunderbird-debuginfo
thunderbird
firefox (Red Hat package)
thunderbird (Red Hat package)
MozillaFirefox-devel
MozillaFirefox-translations-common
MozillaFirefox-debugsource
MozillaFirefox
MozillaFirefox-debuginfo
MozillaThunderbird-debugsource
MozillaThunderbird-debuginfo
MozillaThunderbird-translations-other
MozillaThunderbird
MozillaThunderbird-translations-common
MozillaFirefox-translations-other
Mozilla Thunderbird

The vulnerability allows a remote attacker to execute arbitrary code.

The vulnerability exists due to use-after-free in the Networking: HTTP component when handling HTTP content. A remote attacker can send crafted content to execute arbitrary code.

Install security update from vendor's website.

• https://www.mozilla.org/en-US/security/advisories/mfsa2026-59/
• https://bugzilla.mozilla.org/show_bug.cgi?id=2036929
• https://www.mozilla.org/en-US/security/advisories/mfsa2026-58/
• https://www.mozilla.org/en-US/security/advisories/mfsa2026-57/