Chris Coulson discovered several vulnerabilities in libssh2, a SSH2 client-side library, which could result in denial of service, information leaks or the execution of arbitrary code.
For the stable distribution (stretch), these problems have been fixed in version 1.7.0-1+deb9u1.
We recommend that you upgrade your libssh2 packages.
Further information about Debian Security Advisories, how to apply these updates to your system and frequently asked questions can be found at: https://www.debian.org/security/