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CVE-2018-18509
A flaw during verification of certain S/MIME signatures causes emails to be shown in Thunderbird as having a valid digital signature, even…
Medium5.3EPSS 1.7%
- Published
- Updated
- Reserved
- Assigned by
- mozilla
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.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| NVDNVD · Modified | 3.0 | Medium5.3 | CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N |
- EPSS (exploitation in 30 days)
- 1.7% · top 23% of all CVEs (6 Nov 2026)
Loading the EPSS history…
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.3.
Weakness
- S/MIME signature spoofing
- CWE-347 (opens in a new tab)All about CWE-347 and its CVEs
Affected products
- affected unspecified – < 60.5.1
References (9)
- openSUSE-SU-2019:1162 (opens in a new tab)vendor-advisoryx_refsource_SUSEx_transferred
- https://www.mozilla.org/security/advisories/mfsa2019-06/ (opens in a new tab)x_refsource_MISCx_transferred
- https://bugzilla.mozilla.org/show_bug.cgi?id=1507218 (opens in a new tab)x_refsource_MISCx_transferred
- [oss-security] 20190430 Spoofing OpenPGP and S/MIME Signatures in Emails (multiple clients) (opens in a new tab)mailing-listx_refsource_MLISTx_transferred
- 20190430 OpenPGP and S/MIME signature forgery attacks in multiple email clients (opens in a new tab)mailing-listx_refsource_FULLDISCx_transferred
- http://packetstormsecurity.com/files/152703/Johnny-You-Are-Fired.html (opens in a new tab)x_refsource_MISCx_transferred
- RHSA-2019:1144 (opens in a new tab)vendor-advisoryx_refsource_REDHATx_transferred
- https://github.com/RUB-NDS/Johnny-You-Are-Fired (opens in a new tab)x_refsource_MISCx_transferred
- https://github.com/RUB-NDS/Johnny-You-Are-Fired/blob/master/paper/johnny-fired.pdf (opens in a new tab)x_refsource_MISCx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2018-18509)Record last updated .