Semaphore UI through 2.19.16 RCE via Task Environment Ansible Variable Override

Summary

Semaphore UI through 2.19.16 contains a remote code execution vulnerability that allows users with the task_runner role to override protected Ansible variables by supplying arbitrary keys in the task environment JSON. Attackers can POST tasks setting ansible_ssh_common_args with a ProxyCommand or ansible_connection=local to execute commands as the Semaphore server user, exposing encryption keys, SSH keys and stored secrets.

Evidence

Reported to the maintainer with a proof of concept that reproduced against the affected release.

Remediation

No fixed release is listed in the advisory. Check the references for upstream status.

References

• VulnCheck advisoryhttps://www.vulncheck.com/advisories/semaphore-ui-through-2.19.16-rce-via-task-environment-ansible-variable-override
• Fix pull requesthttps://github.com/semaphoreui/semaphore/pull/3888
• Vulnerable codehttps://github.com/semaphoreui/semaphore/blob/v2.19.16/services/tasks/TaskRunner.go#L395-L431
• Vulnerable codehttps://github.com/semaphoreui/semaphore/blob/v2.19.16/api/projects/tasks.go#L39-L75
• CVE recordhttps://www.cve.org/CVERecord?id=CVE-2026-112305