Critical severity · published Sep 15, 2026
CVE-2026-92240
Out-of-bounds read in IMAP response parser
9.1
CVSS
0.6%
EPSS
No
On KEV
Description
A malicious or compromised IMAP server can trigger an out-of-bounds read in the IMAP response parser by sending an untagged '* ID' response, crashing Thunderbird. The affected parsing path is reachable before authentication. 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:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.6% · higher than 50% 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-2026-92240
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-92240
Permissions Required
https://bugzilla.mozilla.org/show_bug.cgi?id=2069113
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/
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