Unescaped path parameters in AshTypescript generated TypeScript client allow request redirection

Summary

URL Redirection to Untrusted Site ('Open Redirect') vulnerability in ash-project ash_typescript allows an attacker who controls a path-parameter value to redirect a generated client's request, and the credentials attached to it, to an unintended route or an external origin. The URL builders in lib/ash_typescript/typed_controller/codegen/route_renderer.ex replace each :param placeholder with a bare template interpolation and never call encodeURIComponent, so the value reaches executeTypedControllerRequest raw. A value containing ../ is normalised away by the fetch URL resolver and reaches a different route, while ? or # truncates the path and can smuggle or override query parameters. For a route whose path begins with a parameter, a value such as /evil.example.com/x yields the protocol-relative URL //evil.example.com/x, sending the request and the credentials from TypedControllerConfig to an attacker-controlled host. Nothing constrains the value at runtime: get_path_param_type/2 emits only a TypeScript type, which is erased. The query-string path is unaffected, since URLSearchParams.set encodes its own values. This issue affects ash_typescript: from 0.15.0 before 0.18.0.

Timeline

1. Sep 1, 2026, 2:09 AM UTCCVE published
2. Sep 1, 2026, 3:13 PM UTCCISA SSVC assessment

   Exploitation: poc · Automatable: no · Technical impact: partial

3. Sep 1, 2026, 3:13 PM UTCRecord last updated

Affected versions

• ash_typescript

  From 0.15.0 · fixed in 0.18.0

• ash-project/ash_typescript

  Version range not reported

References 4