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Vulnerability · Published Oct 13, 2026 · Assigned by mozilla

CVE-2026-109734Mitigation bypass in the DOM: Security component

High 8.1

In plain English

A high-severity security flaw in Firefox from Mozilla. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 28% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.1High
Exploit odds (30 days)0.3%top 72.4% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
AlmaLinux:9thunderbird153.5.0-1.el9_8.alma.1ALSA-2026:93443
Debian:12firefox-esr153.5.0esr-1~deb12u1DEBIAN-CVE-2026-109734
Debian:13firefox-esr153.5.0esr-1~deb13u1DEBIAN-CVE-2026-109734
Debian:14firefox-esr153.5.0esr-1DEBIAN-CVE-2026-109734
Debian:12thunderbird1:153.5.1esr-1~deb12u1DEBIAN-CVE-2026-109734
Debian:13thunderbird1:153.5.1esr-1~deb13u1DEBIAN-CVE-2026-109734
Debian:14thunderbird1:153.5.0esr-1DEBIAN-CVE-2026-109734
Rocky Linux:9thunderbird0:153.5.0-1.el9_8RLSA-2026:93443
Ubuntu:22.04:LTSmozjs102no fix listedUBUNTU-CVE-2026-109734
Ubuntu:24.04:LTSmozjs102no fix listedUBUNTU-CVE-2026-109734
Ubuntu:24.04:LTSmozjs115no fix listedUBUNTU-CVE-2026-109734
Ubuntu:22.04:LTSmozjs78no fix listedUBUNTU-CVE-2026-109734
Ubuntu:22.04:LTSmozjs91no fix listedUBUNTU-CVE-2026-109734
Ubuntu:22.04:LTSthunderbirdno fix listedUBUNTU-CVE-2026-109734

Affected products (as reported)

VendorProductVersions
Mozilla Firefox see references
Mozilla Thunderbird see references

Weakness: CWE-693 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N

References