DSA-5591-1 libssh – security update

Debian Security Advisory

Several vulnerabilities were discovered in libssh, a tiny C SSH library.


It was reported that using the ProxyCommand or the ProxyJump feature
may allow an attacker to inject malicious code through specially
crafted hostnames.


Jack Weinstein reported that missing checks for return values for
digests may result in denial of service (application crashes) or
usage of uninitialized memory.


Fabian Baeumer, Marcus Brinkmann and Joerg Schwenk discovered that
the SSH protocol is prone to a prefix truncation attack, known as
the “Terrapin attack”. This attack allows a MITM attacker to effect
a limited break of the integrity of the early encrypted SSH
transport protocol by sending extra messages prior to the
commencement of encryption, and deleting an equal number of
consecutive messages immediately after encryption starts.

Details can be found at https://terrapin-attack.com/