USN-6585-1: libssh2 vulnerability

Fabian Bäumer, Marcus Brinkmann, Jörg Schwenk discovered that the SSH
protocol was vulnerable to a prefix truncation attack. If a remote attacker
was able to intercept SSH communications, extension negotiation messages
could be truncated, possibly leading to certain algorithms and features
being downgraded. This issue is known as the Terrapin attack. This update
adds protocol extensions to mitigate this issue.

algorithms attack attacker communications extension extensions fabian bäumer features intercept issue jörg schwenk marcus marcus brinkmann messages negotiation protocol ssh ssh communications ssh protocol terrapin terrapin attack truncated update usn vulnerability vulnerable