Red Hat: incomplete denylist

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.