CVE-2026-101899: Axios: CIDR-form NO_PROXY entries are ignored, causing proxy exclusion bypass for internal IP ranges

Axios supports proxy environment variables and evaluates NO_PROXY exclusions in the Node.js adapter. CIDR-form NO_PROXY entries such as 127.0.0.0/8, 10.0.0.0/8, or 169.254.169.254/32 are not interpreted as IP ranges. As a result, a request to an IP address inside a configured CIDR exclusion can still be sent through the configured proxy.

This affects deployments that rely on CIDR notation to keep loopback, private, Kubernetes, CI, or cloud metadata traffic away from proxy infrastructure.

Axios 1.17.0 honors HTTP_PROXY / HTTPS_PROXY and supports NO_PROXY host exclusions, but CIDR-form NO_PROXY entries such as 127.0.0.0/8 are not treated as network ranges. As a result, requests to IPs covered by a configured CIDR exclusion may still be sent through the configured proxy.

In the attached PoC, a request to 127.0.0.1 is sent through HTTP_PROXY despite NO_PROXY=127.0.0.0/8.

This can cause proxy exclusion bypass in environments where operators use CIDR notation to exclude loopback, private, internal, Kubernetes, CI, or cloud metadata address ranges from proxying.