Vulnerability · Published Sep 29, 2026 · Assigned by mozilla
CVE-2026-100811Sandbox escape due to use-after-free in the DOM: Core & HTML component
Critical 9.6
In plain English
A critical-severity use-after-free 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 18% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)9.6Critical
Exploit odds (30 days)0.3%top 81.5% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
Sandbox escape due to use-after-free in the DOM: Core & HTML component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, and Firefox ESR 140.17.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux:10 | firefox | 140.17.0-1.el10_2 | ALSA-2026:76764 |
| AlmaLinux:8 | firefox | 140.17.0-1.el8_10.alma.1 | ALSA-2026:76850 |
| AlmaLinux:9 | firefox | 140.17.0-1.el9_8.alma.1 | ALSA-2026:76761 |
| AlmaLinux:9 | firefox-x11 | 140.17.0-1.el9_8.alma.1 | ALSA-2026:76761 |
| AlmaLinux:10 | thunderbird | 140.17.0-1.el10_2.alma.1 | ALSA-2026:80674 |
| AlmaLinux:8 | thunderbird | 140.17.0-1.el8_10.alma.1 | ALSA-2026:90913 |
| AlmaLinux:9 | thunderbird | 140.17.0-1.el9_8.alma.1 | ALSA-2026:80694 |
| Debian:12 | firefox-esr | 153.4.0esr-1~deb12u1 | DEBIAN-CVE-2026-100811 |
| Debian:13 | firefox-esr | 153.4.0esr-1~deb13u1 | DEBIAN-CVE-2026-100811 |
| Debian:14 | firefox-esr | 153.4.0esr-1 | DEBIAN-CVE-2026-100811 |
| Debian:12 | thunderbird | 1:140.17.0esr-1~deb12u1 | DEBIAN-CVE-2026-100811 |
| Debian:13 | thunderbird | 1:140.17.0esr-1~deb13u1 | DEBIAN-CVE-2026-100811 |
| Debian:14 | thunderbird | 1:153.4.0esr-1 | DEBIAN-CVE-2026-100811 |
| Rocky Linux:10 | firefox | 0:140.17.0-1.el10_2 | RLSA-2026:76764 |
| Rocky Linux:8 | firefox | 0:140.17.0-1.el8_10 | RLSA-2026:76850 |
| Rocky Linux:9 | firefox | 0:140.17.0-1.el9_8 | RLSA-2026:76761 |
| Rocky Linux:10 | thunderbird | 0:140.17.0-1.el10_2 | RLSA-2026:80674 |
| Rocky Linux:8 | thunderbird | 0:140.17.0-1.el8_10 | RLSA-2026:90913 |
| Rocky Linux:9 | thunderbird | 0:140.17.0-1.el9_8 | RLSA-2026:80694 |
| Ubuntu:22.04:LTS | mozjs102 | no fix listed | UBUNTU-CVE-2026-100811 |
| Ubuntu:24.04:LTS | mozjs102 | no fix listed | UBUNTU-CVE-2026-100811 |
| Ubuntu:24.04:LTS | mozjs115 | no fix listed | UBUNTU-CVE-2026-100811 |
| Ubuntu:22.04:LTS | mozjs78 | no fix listed | UBUNTU-CVE-2026-100811 |
| Ubuntu:22.04:LTS | mozjs91 | no fix listed | UBUNTU-CVE-2026-100811 |
| Ubuntu:22.04:LTS | thunderbird | no fix listed | UBUNTU-CVE-2026-100811 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Thunderbird | see references |
| Mozilla | Firefox | see references |
Weakness: CWE-416 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=2067973
- https://www.mozilla.org/security/advisories/mfsa2026-100/
- https://www.mozilla.org/security/advisories/mfsa2026-101/
- https://www.mozilla.org/security/advisories/mfsa2026-102/
- https://www.mozilla.org/security/advisories/mfsa2026-103/
- https://www.mozilla.org/security/advisories/mfsa2026-97/
- https://www.mozilla.org/security/advisories/mfsa2026-99/