Description
Net::LibSSH versions before 0.004 for Perl authenticate to an unverified server because connect never checks the host key against known_hosts. connect reports success as soon as ssh_connect returns SSH_OK. libssh leaves the known-hosts check to the application, and this binding never makes it, so the strict_hostkeycheck and knownhosts options are set on the session and then decide nothing. Password, agent and public-key authentication, channel and SFTP operations all run on a session whose peer was never identified, so an attacker who can redirect the connection receives the password when password authentication is used, and commands and data sent over the session.
References3
Metrics
- CVSS 3.1
-
9.1
CRITICAL
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N - EPSS — exploit probability
- 0% percentile: 39 · as of 8 November 2026
- CWE
- CWE-322
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.