Critical severity · published Sep 29, 2026
CVE-2026-100781
Sandbox escape due to incorrect boundary conditions in the Graphics: WebRender component
9.6
CVSS
0.3%
EPSS
No
On KEV
Description
Sandbox escape due to incorrect boundary conditions in the Graphics: WebRender 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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
High
Integrity
High
Availability
High
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 26% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FI
Firefox · Mozilla
before 157.0.0; 115.1.0 before 115.42.0; 140.0 before 140.17.0; 153.0 before 153.4.0 · source: NVD
TH
Thunderbird · Mozilla
before 157.0; 140.0 before 140.17.0; 153.0 before 153.4.0 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-100781
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-100781
bugzilla.mozilla.org
https://bugzilla.mozilla.org/show_bug.cgi?id=2068434
www.mozilla.org
https://www.mozilla.org/security/advisories/mfsa2026-100/
www.mozilla.org
https://www.mozilla.org/security/advisories/mfsa2026-101/
www.mozilla.org
https://www.mozilla.org/security/advisories/mfsa2026-102/
www.mozilla.org
https://www.mozilla.org/security/advisories/mfsa2026-103/
www.mozilla.org
https://www.mozilla.org/security/advisories/mfsa2026-97/
More from Firefox
10.0
CVE-2019-11708
Mozilla Firefox and Thunderbird Sandbox Escape Vulnerability
9.8
CVE-2024-9680
Mozilla Firefox Use-After-Free Vulnerability
9.8
CVE-2010-3765
Mozilla Multiple Products Remote Code Execution Vulnerability
9.6
CVE-2022-26486
Mozilla Firefox Use-After-Free Vulnerability
8.8
CVE-2023-5217
Google Chromium libvpx Heap Buffer Overflow Vulnerability