The remote Debian host is missing a security-related update.
Multiple vulnerabilities were discovered in cURL, an URL transfer library. - CVE-2019-5436 A heap buffer overflow in the TFTP receiving code was discovered, which could allow DoS or arbitrary code execution. This only affects the oldstable distribution (stretch). - CVE-2019-5481 Thomas Vegas discovered a double-free in the FTP-KRB code, triggered by a malicious server sending a very large data block. - CVE-2019-5482 Thomas Vegas discovered a heap buffer overflow that could be triggered when a small non-default TFTP blocksize is used.
Upgrade the curl packages. For the oldstable distribution (stretch), these problems have been fixed in version 7.52.1-5+deb9u10. For the stable distribution (buster), these problems have been fixed in version 7.64.0-4+deb10u1.