GHSA-43fc-v873-qw85 Waku has an Open Redirect via `unstable_redirect` Helper
SummaryThe `unstable_redirect()` helper exported from `waku/router/server` (`packages/waku/src/router/define-router.tsx:156–161`) accepts an arbitrary string and reflects it unchanged into the HTTP `Location` response header with no URL validation, scheme restriction, or path-only enforcement. Any application that passes user-controlled input to this helper — the natural pattern documented in the JSDoc and official fixtures — is vulnerable to open redirect attacks. An attacker who convinces a victim to click a crafted link can silently redirect the browser to an arbitrary external domain, enabling phishing, credential harvesting, and OAuth token theft. Additionally, scheme-relative URLs (`//evil.example/`) bypass naive `https?://`-only allow-list filters that developers might add as ad-hoc mitigations.Dynamic PoC confirmed against **waku 1.0.0-beta.0** (commit `8e9f542`) in an isolated Docker environment. Two independent dynamic runs produced identical results.Root Cause`packages/waku/src/router/define-router.tsx:156–161`:The JSDoc comment states "only URL `pathname` is supported", but this constraint is expressed as documentation only — the function performs **no validation**. The `location` value propagates via `createCustomError` (`custom-errors.ts:22–26`) into an error digest, is recovered by `getErrorInfo` in the request handler (`handler.ts:79–89`), and reflected directly into `headers.location` of the outgoing `Response` with no sanitization:Trigger (one-line summary)Any developer-supplied user input passed to `unstable_redirect()` is reflected unchanged into the HTTP `Location` header, enabling navigation to an attacker-controlled domain.Affected Entry Surfaces`unstable_redirect(location, status?)` — `waku/router/server` public exportAny page/route component that passes `searchParams`, `query`, or other user-
controlled strings to `unstable_redirect` (the standard post-login or callback
redirect pattern)All waku adapters (Node.js, Cloudflare Workers, Vercel Edge, Deno) share the same
`handler.ts` reflection path; cross-runtime CRLF parity is unaudited (see note
below)Additional Defense-in-Depth ConcernOn Node.js, CRLF injection via the `Location` header is rejected by `node:_http_outgoing.setHeader` (`ERR_INVALID_CHAR`). This defense is **platform-specific** and not present in the waku source. Cloudflare Workers, Deno Deploy, and other edge runtimes have not been verified to offer equivalent protection. A cross-runtime audit is recommended.Suggested Fix OutlineValidate the `location` argument inside `unstable_redirect` before the error is thrown: reject any value that does not begin with a single `/` (no `//`), and reject any value containing control characters (`\x00`–`\x1f`). An opt-in allow-list for intentional cross-origin redirects can be provided via a framework configuration option.Disclosure| Field            | Value                              |
|------------------|------------------------------------|
| Reporter         | j0hndo (`dohyun4466@gmail.com`)    |
| Discovery date   | 2026-05-17                         |
| Embargo          | 90 days from acknowledgment        |
| Patched version  | Not yet available                  |
| Public references| CWE-601; OWASP A01:2021            |
CVSS v3.1 score: 3.1