CVE-2026-84714: Incomplete List of Disallowed Inputs

A flaw was found in the automation-controller input-validation guard sanitize_jinja(). The function uses two regular expressions to reject user-supplied Jinja, but the patterns stop at the first interior '}' or '%' character, so a Jinja expression containing an inner brace (for example an empty dict) is accepted while remaining valid Jinja. Because sanitize_jinja() is the sole guard on several launch-time fields — ad-hoc command module_args, Machine-credential username / become_method / become_user, and inventory host names — a low-privileged user can inject Jinja that ansible-core evaluates in the execution environment. This enables execution of arbitrary commands in the execution environment (bypassing an administrator's AD_HOC_COMMANDS module allowlist) and disclosure of secrets belonging to credentials the attacker cannot read (by templating a co-attached credential's injected environment variables), across the credential access-control boundary.