What is CVE-2019-11739?

CVE-2019-11739 is a medium-severity vulnerability in Mozilla Thunderbird, classified under Cleartext Transmission of Sensitive Information. CVSS score: 6.5/10. Published 2019-09-27.

How severe is CVE-2019-11739?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Vulnerability in Mozilla Thunderbird

CVE-2019-11739

Encrypted S/MIME parts in a crafted multipart/alternative message can leak plaintext when included in a a HTML reply/forward. This vulnerability affects Thunderbird < 68.1 and Thunderbird < 60.9.

Published 2019-09-27 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.009 (58.1th percentile), scored 2026-10-01.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 58th percentile — 58.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.009 · newest: 0.009 · change: 0.000

Affected products

Mozilla Thunderbird — versions unspecified, unspecified

Weakness classification (CWE)

CWE-319 — Cleartext Transmission of Sensitive Information

References

bugzilla.mozilla.org/show_bug.cgi (Permissions Required, Issue Tracking, Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2019-29/ (Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2019-30/ (Vendor Advisory)
lists.opensuse.org/opensuse-security-announce/2019-10/msg00010.html (vendor-advisory)
lists.opensuse.org/opensuse-security-announce/2019-10/msg00009.html (vendor-advisory)
usn.ubuntu.com/4150-1/ (vendor-advisory)

Frequently asked questions

What is CVE-2019-11739?: CVE-2019-11739 is a medium-severity vulnerability in Mozilla Thunderbird, classified under Cleartext Transmission of Sensitive Information. CVSS score: 6.5/10. Published 2019-09-27.
How severe is CVE-2019-11739?: Medium severity. CVSS v3 base score is 6.5 out of 10.