High severity · published Aug 18, 2026
CVE-2026-74953
Privilege escalation in the Networking: Cookies component
8.8
CVSS
0.4%
EPSS
No
On KEV
Description
Privilege escalation in the Networking: Cookies component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 38% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FI
Firefox · Mozilla
before 140.14.0; 141.0.0 before 153.1.0 · source: NVD
TH
Thunderbird · Mozilla
before 140.14.0; 141.0 before 153.1.0 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-74953
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-74953
Permissions Required
https://bugzilla.mozilla.org/show_bug.cgi?id=2022382
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-74/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-76/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-77/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-78/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-79/
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