Critical severity · published Sep 15, 2026
CVE-2026-92238
Ambiguous parsing of mail headers
9.8
CVSS
0.5%
EPSS
No
On KEV
Description
A maliciously constructed mail header could lead to multiple fields being parsed as one, or potential memory safety violations. This vulnerability was fixed in Thunderbird 156, Thunderbird 140.16, and Thunderbird 153.3.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 45% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
TH
Thunderbird · Mozilla
before 140.16.0; 141.0 before 153.3.0; 154.0 before 156.0 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-92238
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-92238
Permissions Required
https://bugzilla.mozilla.org/show_bug.cgi?id=2060601
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-94/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-95/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-96/
More from Thunderbird
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