GHSA-jqh4-m9w3-8hp9: Axios: Fetch adapter `ReadableStream` uploads bypass `maxBodyLength`

Summary axios’ fetch adapter does not enforce maxBodyLength for live WHATWG ReadableStream request bodies whose size cannot be determined before dispatch. Applications that use adapter: "fetch" and rely on maxBodyLength to cap untrusted upload/proxy streams can send the full stream even when it exceeds the configured limit. This affects fetch-adapter usage in edge runtimes where fetch is selected, and in Node.js or browser environments where the fetch adapter is explicitly selected. The HTTP adapter’s stream upload path is not affected. Impact An attacker who can supply or influence a streamed request body can bypass the caller’s configured upload-size limit. Practical impact is unexpected outbound network egress, request-level resource consumption, and possible exhaustion of upstream API quotas or bandwidth. This does not expose response data, execute code, or modify axios configuration. Exploitability depends on an application passing attacker-controlled, unknown-length stream data to axios and relying on maxBodyLength as the size guard. Affected Functionality Affected: - adapter: "fetch" or environments where axios selects the fetch adapter. - Request methods with bodies, such as POST, PUT, and PATCH. - data as a WHATWG ReadableStream without a reliable Content-Length. - Configurations that set maxBodyLength to a finite value. Not affected: - Axios versions before the fetch adapter was introduced. - The Node HTTP adapter stream enforcement path. - Known-length fetch-adapter bodies in 1.16.0+, such as strings, Blob, ArrayBuffer, ArrayBufferView, URLSearchParams, spec-compliant FormData, or requests with a finite Content-Length. Technical Details In lib/adapters/fetch.js, getBodyLength() handles null bodies, Blob, spec-compliant FormData, ArrayBuffer values, URLSearchParams, and strings. It has no branch for ReadableStream, so resolveBodyLength(headers, data) returns undefined when no finite Content-Length header is present. The maxBodyLength check only