The json_repair library's SchemaRepairer.resolve_schema() method processes JSON Schema $ref pointers in a while loop without detecting cycles. When a schema contains a circular $ref, such as a reference pointing to itself, the loop never terminates because the same dictionary object is repeatedly returned by _resolve_ref(). This leads to unbounded CPU usage and a denial of service. The vulnerability is reachable without authentication through the demo Flask API, which accepts attacker-controlled schemas with minimal validation. The recommended fix is to add cycle detection by tracking visited schema objects and raising an error upon detecting a circular reference.

An attacker can cause a worker process using json_repair to consume CPU indefinitely by submitting a crafted JSON Schema with circular $ref references. This results in a denial of service condition, making the service unresponsive. No authentication is required to exploit this via the publicly accessible demo API. There is no impact on confidentiality or integrity reported, only availability is affected.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. The recommended fix involves adding cycle detection in resolve_schema() to raise an error when a circular $ref is detected, preventing infinite loops. Until a patch is available, avoid processing untrusted schemas or implement external safeguards such as request timeouts or input validation to detect circular references.