CVE 2021-21439

DoS attack can be performed when an email contains specially designed URL in the body. It can lead to the high CPU usage and cause low quality of service, or in extreme case bring the system to a halt. This issue affects: OTRS AG ((OTRS)) Community Edition 6.0.x version 6.0.1 and later versions. OTRS AG OTRS 7.0.x version 7.0.26 and prior versions; 8.0.x version 8.0.13 and prior versions.

See the CVE page on Mitre.org for more details.