Critical severity · published Sep 29, 2026
CVE-2026-100787
Sandbox escape in the XUL component
9.6
CVSS
0.3%
EPSS
No
On KEV
Description
Sandbox escape in the XUL component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157.
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 23% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FI
Firefox · Mozilla
before 153.4.0; 154.0.0 before 157.0.0 · source: NVD
TH
Thunderbird · Mozilla
before 153.4.0; 154.0 before 157.0 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-100787
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-100787
bugzilla.mozilla.org
https://bugzilla.mozilla.org/show_bug.cgi?id=2071068
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/mfsa2026-103/
www.mozilla.org
https://www.mozilla.org/security/advisories/mfsa2026-97/
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