Critical severity · published Aug 18, 2026
CVE-2026-75874
Sandbox escape in the Remote Settings Client component
10.0
CVSS
0.5%
EPSS
No
On KEV
Description
Sandbox escape in the Remote Settings Client component. This vulnerability was fixed in Firefox 154, Thunderbird 154, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 140.15, and Thunderbird 153.2.
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 39% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FI
Firefox · Mozilla
before 154.0.0 · source: NVD
TH
Thunderbird · Mozilla
before 154.0 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-75874
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-75874
Permissions Required
https://bugzilla.mozilla.org/show_bug.cgi?id=2039972
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-74/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-78/
www.mozilla.org
https://www.mozilla.org/security/advisories/mfsa2026-83/
www.mozilla.org
https://www.mozilla.org/security/advisories/mfsa2026-84/
www.mozilla.org
https://www.mozilla.org/security/advisories/mfsa2026-85/
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