Axios is a promise-based HTTP client for the browser and Node.js. From 1.15.0 until 1.20.0, Axios shouldBypassProxy applies a quadratic trailing-dot regular expression to redirect hostnames. HTTP_PROXY or HTTPS_PROXY is configured, NO_PROXY or no_proxy is non-empty, redirects are followed, and a crafted redirect Location contains many dots followed by a non-dot character. Hostname.replace(/.+$/, '') backtracks quadratically while processing the crafted redirect hostname. Synchronous regular-expression processing can block the Node.js event loop and cause denial of service. This issue is fixed in version 1.20.0.