Out-of-bounds Read in Mozilla Thunderbird
CVE-2026-92240
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.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H.
EPSS exploit prediction
EPSS: 0.006 (50.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 50th percentile — 50.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: 0.000
Affected products
Weakness classification (CWE)
References
- bugzilla.mozilla.org/show_bug.cgi (Permissions Required)
- www.mozilla.org/security/advisories/mfsa2026-95/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-94/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-96/ (Vendor Advisory)
Frequently asked questions
- What is CVE-2026-92240?
- CVE-2026-92240 is a critical-severity vulnerability in Mozilla Thunderbird, classified under Out-of-bounds Read. CVSS score: 9.1/10. Published 2026-09-15.
- How severe is CVE-2026-92240?
- Critical severity. CVSS v3 base score is 9.1 out of 10.