The remote Debian host is missing a security-related update.
Several vulnerabilities were discovered in Apache Traffic Server, a reverse and forward proxy server. They could lead to the use of an incorrect upstream proxy, or allow a remote attacker to cause a denial-of-service by application crash.
Upgrade the trafficserver packages. For the stable distribution (stretch), these problems have been fixed in version 7.0.0-6+deb9u1.