The remote host is vulnerable to a Denial of Service (DoS) attack.
The remote host is running Sympa, a mailing list manager. This version of Sympa is reported to be vulnerable to a Denial-of-Service flaw stemming from an inability to properly parse user-supplied 'Content-Type' headers. An attacker exploiting this flaw would send a malformed request to the server, causing the service to fail.
Upgrade to version 5.4 or higher.