CVE-2026-100818
published 2026-09-29CVE-2026-100818: Sandbox escape due to use-after-free in the Widget: Gtk component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17…
PriorityP347critical9.6CVSS 3.1
AVNACLPRNUIRSCCHIHAH
EPSS
0.26%
16.5th percentile
Sandbox escape due to use-after-free in the Widget: Gtk 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
16 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| mozilla | firefox | < Firefox 157 | Firefox 157 |
| mozilla | firefox | < 140.17.0 | 140.17.0 |
| mozilla | firefox | — | — |
| mozilla | firefox | >= 141.0 < 153.4.0 | 153.4.0 |
| mozilla | firefox | >= 154.0.0 < 157.0.0 | 157.0.0 |
| mozilla | firefox_esr | < Firefox ESR 153.4 | Firefox ESR 153.4 |
| mozilla | firefox_esr | < Firefox ESR 140.17 | Firefox ESR 140.17 |
| mozilla | thunderbird | < Thunderbird 153.4 | Thunderbird 153.4 |
| mozilla | thunderbird | < Thunderbird 140.17 | Thunderbird 140.17 |
| mozilla | thunderbird | < Thunderbird 157 | Thunderbird 157 |
| mozilla | thunderbird | < 140.17.0 | 140.17.0 |
| mozilla | thunderbird | — | — |
| mozilla | thunderbird | >= 141.0 < 153.4.0 | 153.4.0 |
| mozilla | thunderbird | >= 154.0 < 157.0 | 157.0 |
| rhel10 | firefox-flatpak | — | — |
| rhel10 | thunderbird-flatpak | — | — |
CVSS provenance
nvdv3.19.6CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
vendor_redhat9.6CRITICAL
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GHSA
Sandbox escape due to use-after-free in the Widget: Gtk component.
ghsa_unreviewed·2026-09-29
CVE-2026-100818 [CRITICAL] CWE-416 Sandbox escape due to use-after-free in the Widget: Gtk component.
Sandbox escape due to use-after-free in the Widget: Gtk component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, and Firefox ESR 140.17.
Red Hat
firefox: thunderbird: Sandbox escape due to use-after-free in the Widget: Gtk component
vendor_redhat·2026-09-29·CVSS 9.6
CVE-2026-100818 [CRITICAL] CWE-825 firefox: thunderbird: Sandbox escape due to use-after-free in the Widget: Gtk component
firefox: thunderbird: Sandbox escape due to use-after-free in the Widget: Gtk component
Sandbox escape due to use-after-free in the Widget: Gtk 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.
A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue:
Sandbox escape due to use-after-free in the Widget: Gtk component
Statement: Red Hat Product Security rates the severity of this flaw as determined by the Mozilla Foundation Security Advisory.
Package: firefox (Red Hat Enterprise Linux 10) - Affected
Package: rhel10/firefox-flatpak (Red Hat Enterprise Linux 10) - Affected
Package: rhel10/thunderbird-flatpak (Red Hat Enterpr
Mozilla
Mozilla Foundation Security Advisory 2026-97: CVE-2026-100818
vendor_mozilla·CVSS 9.6
CVE-2026-100818 [CRITICAL] Mozilla Foundation Security Advisory 2026-97: CVE-2026-100818
Mozilla Foundation Security Advisory 2026-97
CVE: CVE-2026-100818
Product: Firefox
Impact: low
Fixed in: Firefox 157
Mozilla
Mozilla Foundation Security Advisory 2026-103: CVE-2026-100818
vendor_mozilla·CVSS 9.6
CVE-2026-100818 [CRITICAL] Mozilla Foundation Security Advisory 2026-103: CVE-2026-100818
Mozilla Foundation Security Advisory 2026-103
CVE: CVE-2026-100818
Product: Thunderbird
Impact: low
Fixed in: Thunderbird 153.4
Mozilla
Mozilla Foundation Security Advisory 2026-102: CVE-2026-100818
vendor_mozilla·CVSS 9.6
CVE-2026-100818 [CRITICAL] Mozilla Foundation Security Advisory 2026-102: CVE-2026-100818
Mozilla Foundation Security Advisory 2026-102
CVE: CVE-2026-100818
Product: Thunderbird
Impact: moderate
Fixed in: Thunderbird 140.17
Mozilla
Mozilla Foundation Security Advisory 2026-100: CVE-2026-100818
vendor_mozilla·CVSS 9.6
CVE-2026-100818 [CRITICAL] Mozilla Foundation Security Advisory 2026-100: CVE-2026-100818
Mozilla Foundation Security Advisory 2026-100
CVE: CVE-2026-100818
Product: Firefox ESR
Impact: low
Fixed in: Firefox ESR 153.4
Mozilla
Mozilla Foundation Security Advisory 2026-101: CVE-2026-100818
vendor_mozilla·CVSS 9.6
CVE-2026-100818 [CRITICAL] Mozilla Foundation Security Advisory 2026-101: CVE-2026-100818
Mozilla Foundation Security Advisory 2026-101
CVE: CVE-2026-100818
Product: Thunderbird
Impact: low
Fixed in: Thunderbird 157
Mozilla
Mozilla Foundation Security Advisory 2026-99: CVE-2026-100818
vendor_mozilla·CVSS 9.6
CVE-2026-100818 [CRITICAL] Mozilla Foundation Security Advisory 2026-99: CVE-2026-100818
Mozilla Foundation Security Advisory 2026-99
CVE: CVE-2026-100818
Product: Firefox ESR
Impact: moderate
Fixed in: Firefox ESR 140.17
No detection rules found.
No public exploits indexed.
https://bugzilla.mozilla.org/show_bug.cgi?id=2069399https://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/
2026-09-29
Published