CVE-2026-126641 (GCVE-0-2026-126641)

Vulnerability from cvelistv5 – Published: 2026-11-12 10:47 – Updated: 2026-11-12 10:47
VLAI
Title
Ansible-pylibssh: accepts a changed ssh host key when host_key_auto_add is enabled
Summary
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.
Severity
6.5 (Medium)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N
CWE
  • CWE-322 - Key Exchange without Entity Authentication
Assigner
redhat CNA under the redhat root
CNA scorecard B 82/100 over 1188 records in the last 180 days details
References
URL Tags
https://access.redhat.com/security/cve/CVE-2026-126641 vdb-entryx_refsource_REDHAT
https://bugzilla.redhat.com/show_bug.cgi?id=2571719 issue-trackingx_refsource_REDHAT
Impacted products
Vendor Product Version CPE status
Red Hat Red Hat Ansible Automation Platform 2     cpe:/a:redhat:ansible_automation_platform:2
Create a notification for this product.
Date Public
2026-11-11 14:19
Credits
Red Hat would like to thank Satriyo Utomo (aleens-labs) for reporting this issue.
Show details on NVD website
To clipboard 

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