The nono-py Python API contains a vulnerability classified as CWE-1188, where a restrictive-looking configuration for reverse-proxy credential routes is unsafe by default. When the allowed_hosts configuration is empty, nono-proxy implicitly allows all hosts, enabling a sandboxed child process configured with CapabilitySet.proxy_only to bypass intended network restrictions. This results in an authorization bypass and policy confusion, where the actual network access includes arbitrary transparent CONNECT tunnels beyond the nominated routes. The vulnerability affects versions prior to 0.11.0. The impact depends on the environment but can lead to unauthorized outbound network access and potential exfiltration or access to unintended services. The CVSS 3.1 vector is AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N, indicating local attack vector, low complexity, low privileges required, no user interaction, scope changed, and low confidentiality and integrity impacts without availability impact. No patch or official fix is currently documented.

This vulnerability allows a sandboxed child process to bypass intended network access restrictions by exploiting an implicit allow-all policy when allowed_hosts is empty. The child process can use the local proxy as a transparent CONNECT tunnel to reach hosts outside the designated reverse-proxy credential routes. This expands the outbound network reach beyond the intended policy, potentially enabling data exfiltration or unauthorized access to internal or internet services. The impact severity is medium by default but can be high in environments that rely on strict egress controls for untrusted code or sensitive credentials.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, users should avoid configurations with empty allowed_hosts in nono-py and explicitly specify allowed hosts to prevent implicit allow-all behavior. Review and restrict proxy configurations to ensure they do not unintentionally permit broader network access than intended.