CVE-2026-44937: Rancher Fleet has Unauthenticated Webhook: Regex Injection via Unsanitized Repository URL Components

A vulnerability has been identified in Fleet when the webhook endpoint is configured without a secret; an attacker can forge webhook requests. The attacker doesn’t need to know the specific repository or path configured in the GitRepo resource to make Fleet process these requests.

An attacker can exploit this vulnerability to cause the following impacts:

1. Trigger continuous repository re-cloning, which increases network traffic and can deplete resources on the management cluster.
2. Downgrade running services to any historical revision available in the remote Git repository. This risk applies if the attacker has read access to the target Git repository and knows its configured path.

Please consult the associated MITRE ATT&CK - Technique - T1499.004: Endpoint Denial of Service for further information about this category of attack.