If an MQTT v5 client connects to Eclipse Mosquitto versions 1.6.0 to 1.6.4 inclusive, sets a last will and testament, sets a will delay interval, sets a session expiry interval, and the will delay interval is set longer than the session expiry interval, then a use after free error occurs, which has the potential to cause a crash in some situations.

References

• https://nvd.nist.gov/vuln/detail/CVE-2019-11778
• https://bugs.eclipse.org/bugs/show_bug.cgi?id=551162