Critical severity · published Mar 24, 2026
CVE-2026-4692
Sandbox escape in the Responsive Design Mode component
10.0
CVSS
0.5%
EPSS
No
On KEV
Description
Sandbox escape in the Responsive Design Mode component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 43% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FI
Firefox · Mozilla
before 115.34.0; before 149.0; 128.0 before 140.9.0 · source: NVD
TH
Thunderbird · Mozilla
before 140.9.0; before 149.0 · source: NVD
RH
Red Hat Enterprise Linux 10 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 10.0 Extended Update Support · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 6 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 7 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 7 Extended Lifecycle Support · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 8 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 8.2 Advanced Update Support · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support · Red Hat
All versions, or not specified · source: CISA
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-4692
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-4692
Permissions Required
https://bugzilla.mozilla.org/show_bug.cgi?id=2017643
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-20/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-21/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-22/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-23/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-24/
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