What is CVE-2026-92239?

CVE-2026-92239 is a high-severity vulnerability in Mozilla Thunderbird, classified under Out-of-bounds Read. CVSS score: 8.1/10. Published 2026-09-15.

How severe is CVE-2026-92239?

High severity. CVSS v3 base score is 8.1 out of 10.

Out-of-bounds Read in Mozilla Thunderbird

CVE-2026-92239

A maliciously constructed IMAP line could cause an out-of-bounds buffer read. This vulnerability was fixed in Thunderbird 156, Thunderbird 140.16, and Thunderbird 153.3.

Vulnerability class: Buffer Overflow

Published 2026-09-15 · last modified 2026-09-24.

CVSS v3 metric

CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H.

EPSS exploit prediction

EPSS: 0.004 (34.8th percentile), scored 2026-10-31.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 35th percentile — 34.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000

Affected products

Mozilla Thunderbird

Weakness classification (CWE)

CWE-125 — Out-of-bounds Read

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-2026-92239?: CVE-2026-92239 is a high-severity vulnerability in Mozilla Thunderbird, classified under Out-of-bounds Read. CVSS score: 8.1/10. Published 2026-09-15.
How severe is CVE-2026-92239?: High severity. CVSS v3 base score is 8.1 out of 10.