Red Hat Ansible Automation Platform libssh connection plugin Session.verify_knownhost improper authentication

Summaryinfo

A vulnerability classified as critical was found in Red Hat Ansible Automation Platform. The affected element is the function Session.verify_knownhost of the component libssh connection plugin. Such manipulation leads to improper authentication. This vulnerability is referenced as CVE-2026-126641. It is possible to launch the attack remotely. No exploit is available.

Detailsinfo

A vulnerability was found in Red Hat Ansible Automation Platform (version unknown). It has been rated as critical. Affected by this issue is the function Session.verify_knownhost of the component libssh connection plugin. The manipulation with an unknown input leads to a improper authentication vulnerability. Using CWE to declare the problem leads to CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. Impacted is confidentiality, integrity, and availability. CVE summarizes:

A host key verification flaw was found in ansible-pylibssh and in the ansible.netcommon libssh connection plugin. When trust-on-first-use is enabled (host_key_auto_add on the libssh connection plugin, or AutoAddPolicy in ansible-pylibssh), a host that is already present in known_hosts but now presents a different key is accepted without warning. The pylibssh Session.verify_knownhost() method passes the SSH_KNOWN_HOSTS_CHANGED and SSH_KNOWN_HOSTS_OTHER states to the same missing_host_key() policy hook used for unknown hosts, and the bundled AutoAddPolicy/RejectPolicy classes (as well as ansible.netcommon's MyAddPolicy, which is modeled on paramiko's AutoAddPolicy) therefore add the changed key and continue the connection rather than aborting as paramiko's BadHostKeyException path would. As a result the controller authenticates to the substitute host, runs the play there, and appends the new key to known_hosts, which can disclose connection credentials to an attacker performing a machine-in-the-middle attack. Default configurations (host_key_checking enabled, host_key_auto_add unset) are not affected; non-interactive runs fail closed.

The advisory is available at access.redhat.com. This vulnerability is handled as CVE-2026-126641 since 11/11/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Successful exploitation requires user interaction by the victim. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $5k-$25k at the moment (estimation calculated on 11/12/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Type

• Automation Software

Vendor

• Red Hat

Name

• Ansible Automation Platform

License

• open-source

Website

• Vendor: https://www.redhat.com/

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