The remote Debian host is missing a security-related update.
Two vulnerabilities were discovered in cURL, an URL transfer library. - CVE-2018-16839 Harry Sintonen discovered that, on systems with a 32 bit size_t, an integer overflow would be triggered when a SASL user name longer than 2GB is used. This would in turn cause a very small buffer to be allocated instead of the intended very huge one, which would trigger a heap buffer overflow when the buffer is used. - CVE-2018-16842 Brian Carpenter discovered that the logic in the curl tool to wrap error messages at 80 columns is flawed, leading to a read buffer overflow if a single word in the message is itself longer than 80 bytes.
Upgrade the curl packages. For the stable distribution (stretch), these problems have been fixed in version 7.52.1-5+deb9u8.