CVE-2026-100778
published 2026-09-29CVE-2026-100778: 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…
PriorityP347critical9.6CVSS 3.1
AVNACLPRNUIRSCCHIHAH
EPSS
0.32%
23.3th percentile
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, Firefox ESR 115.42, and Firefox ESR 140.17.
Affected
18 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| mozilla | firefox | < Firefox 157 | Firefox 157 |
| mozilla | firefox | — | — |
| mozilla | firefox | >= 115.0.1 < 115.42.0 | 115.42.0 |
| mozilla | firefox | >= 140.0.0 < 140.17.0 | 140.17.0 |
| mozilla | firefox | >= 153.0 < 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 115.42 | Firefox ESR 115.42 |
| 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 | — | — |
| mozilla | thunderbird | >= 140.0 < 140.17.0 | 140.17.0 |
| mozilla | thunderbird | >= 153.0 < 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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Red Hat
firefox: Sandbox escape due to use-after-free in the DOM: Core & HTML component
vendor_redhat·2026-09-29·CVSS 9.6
CVE-2026-100778 [CRITICAL] CWE-825 firefox: Sandbox escape due to use-after-free in the DOM: Core & HTML component
firefox: Sandbox escape due to use-after-free in the DOM: Core & HTML component
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, Firefox ESR 115.42, and Firefox ESR 140.17.
A flaw was found in Firefox. The Mozilla Foundation's Security Advisory describes the following issue:
Sandbox escape due to use-after-free in the DOM: Core & HTML 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 E
Mozilla
Mozilla Foundation Security Advisory 2026-103: CVE-2026-100778
vendor_mozilla·CVSS 9.6
CVE-2026-100778 [CRITICAL] Mozilla Foundation Security Advisory 2026-103: CVE-2026-100778
Mozilla Foundation Security Advisory 2026-103
CVE: CVE-2026-100778
Product: Thunderbird
Impact: low
Fixed in: Thunderbird 153.4
Mozilla
Mozilla Foundation Security Advisory 2026-102: CVE-2026-100778
vendor_mozilla·CVSS 9.6
CVE-2026-100778 [CRITICAL] Mozilla Foundation Security Advisory 2026-102: CVE-2026-100778
Mozilla Foundation Security Advisory 2026-102
CVE: CVE-2026-100778
Product: Thunderbird
Impact: moderate
Fixed in: Thunderbird 140.17
Mozilla
Mozilla Foundation Security Advisory 2026-97: CVE-2026-100778
vendor_mozilla·CVSS 9.6
CVE-2026-100778 [CRITICAL] Mozilla Foundation Security Advisory 2026-97: CVE-2026-100778
Mozilla Foundation Security Advisory 2026-97
CVE: CVE-2026-100778
Product: Firefox
Impact: low
Fixed in: Firefox 157
Mozilla
Mozilla Foundation Security Advisory 2026-100: CVE-2026-100778
vendor_mozilla·CVSS 9.6
CVE-2026-100778 [CRITICAL] Mozilla Foundation Security Advisory 2026-100: CVE-2026-100778
Mozilla Foundation Security Advisory 2026-100
CVE: CVE-2026-100778
Product: Firefox ESR
Impact: low
Fixed in: Firefox ESR 153.4
Mozilla
Mozilla Foundation Security Advisory 2026-98: CVE-2026-100778
vendor_mozilla·CVSS 9.6
CVE-2026-100778 [CRITICAL] Mozilla Foundation Security Advisory 2026-98: CVE-2026-100778
Mozilla Foundation Security Advisory 2026-98
CVE: CVE-2026-100778
Product: Firefox ESR
Impact: moderate
Fixed in: Firefox ESR 115.42
Mozilla
Mozilla Foundation Security Advisory 2026-99: CVE-2026-100778
vendor_mozilla·CVSS 9.6
CVE-2026-100778 [CRITICAL] Mozilla Foundation Security Advisory 2026-99: CVE-2026-100778
Mozilla Foundation Security Advisory 2026-99
CVE: CVE-2026-100778
Product: Firefox ESR
Impact: moderate
Fixed in: Firefox ESR 140.17
Mozilla
Mozilla Foundation Security Advisory 2026-101: CVE-2026-100778
vendor_mozilla·CVSS 9.6
CVE-2026-100778 [CRITICAL] Mozilla Foundation Security Advisory 2026-101: CVE-2026-100778
Mozilla Foundation Security Advisory 2026-101
CVE: CVE-2026-100778
Product: Thunderbird
Impact: low
Fixed in: Thunderbird 157
VulDB
Mozilla Firefox up to 115.41/140.16/153.3/156 DOM Core/HTML use after free (Nessus ID 351394 / WID-SEC-2026-3654)
vuldb·2026-10-03·CVSS 9.6
CVE-2026-100778 [CRITICAL] Mozilla Firefox up to 115.41/140.16/153.3/156 DOM Core/HTML use after free (Nessus ID 351394 / WID-SEC-2026-3654)
A vulnerability classified as critical was found in Mozilla Firefox up to 115.41/140.16/153.3/156. This vulnerability affects unknown code of the component DOM Core/HTML. The manipulation results in use after free.
This vulnerability was named CVE-2026-100778. The attack may be performed from remote. There is no available exploit.
Upgrading the affected component is advised.
GHSA
Sandbox escape due to use-after-free in the DOM: Core & HTML component.
ghsa_unreviewed·2026-09-29
CVE-2026-100778 [CRITICAL] CWE-416 Sandbox escape due to use-after-free in the DOM: Core & HTML component.
Sandbox escape due to use-after-free in the DOM: Core & HTML component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.
No detection rules found.
No public exploits indexed.
https://bugzilla.mozilla.org/show_bug.cgi?id=2068406https://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/mfsa2026-98/https://www.mozilla.org/security/advisories/mfsa2026-99/
2026-09-29
Published