CVE-2018-18509

Name: CVE-2018-18509
Creator: NVD / NIST
Published: 2019-04-26T17:29:00.243+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

UnknownEPSS 1.68%

Last modified Jun 17, 2026

CVE-2018-18509 is a vulnerability of currently unknown severity. A flaw during verification of certain S/MIME signatures causes emails to be shown in Thunderbird as having a valid digital signature, even if the shown message contents aren't covered by the signature. The flaw allows an attacker to reuse a valid S/MIME signature to craft an email message with arbitrary content. EPSS estimates a 1.68% chance of exploitation in the next 30 days.

Description

A flaw during verification of certain S/MIME signatures causes emails to be shown in Thunderbird as having a valid digital signature, even if the shown message contents aren't covered by the signature. The flaw allows an attacker to reuse a valid S/MIME signature to craft an email message with arbitrary content. This vulnerability affects Thunderbird < 60.5.1.

Metrics

EPSS Probability

1.68%

73.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-347

Affected Software

Vendor	Product	Versions
Mozilla	Thunderbird	< 60.5.1

References

http://lists.opensuse.org/opensuse-security-announce/2019-04/msg00043.html
http://packetstormsecurity.com/files/152703/Johnny-You-Are-Fired.htmlThird Party Advisory, VDB Entry
http://seclists.org/fulldisclosure/2019/Apr/38Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2019/04/30/4Mailing List, Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:1144
https://bugzilla.mozilla.org/show_bug.cgi?id=1507218Issue Tracking, Permissions Required, Vendor Advisory
https://github.com/RUB-NDS/Johnny-You-Are-Fired
https://github.com/RUB-NDS/Johnny-You-Are-Fired/blob/master/paper/johnny-fired.pdf
https://www.mozilla.org/security/advisories/mfsa2019-06/Vendor Advisory
http://lists.opensuse.org/opensuse-security-announce/2019-04/msg00043.html
http://packetstormsecurity.com/files/152703/Johnny-You-Are-Fired.htmlThird Party Advisory, VDB Entry
http://seclists.org/fulldisclosure/2019/Apr/38Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2019/04/30/4Mailing List, Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:1144
https://bugzilla.mozilla.org/show_bug.cgi?id=1507218Issue Tracking, Permissions Required, Vendor Advisory
https://github.com/RUB-NDS/Johnny-You-Are-Fired
https://github.com/RUB-NDS/Johnny-You-Are-Fired/blob/master/paper/johnny-fired.pdf
https://www.mozilla.org/security/advisories/mfsa2019-06/Vendor Advisory

Timeline

Published: Apr 26, 2019
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2018-18509?

How severe is CVE-2018-18509?

Severity scoring for CVE-2018-18509 is pending analysis. The EPSS model estimates a 1.68% probability of exploitation in the next 30 days.

How do I fix CVE-2018-18509?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2018-18509?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST