CVE-2026-54290

### Summary With `credentials: true` and no explicit `origin` (the default wildcard), the CORS Middleware reflects the request's `Origin` and sends `Access-Control-Allow-Credentials: true`. Any site can then make credentialed cross-origin requests and read the responses, exposing cookie-authenticated endpoints to arbitrary origins. ### Details The spec forbids `Access-Control-Allow-Origin: *` with credentials and browsers reject it, so this configuration used to fail closed. In affected versions the middleware reflects the request `Origin` instead, so it now succeeds for every origin, including `null`. The preflight also echoes the requested headers back, approving non-simple credentialed requests too. This issue arises when an application enables `credentials: true` and leaves `origin` unset or set to the wildcard. ### Impact Any third-party page a logged-in user visits can read the application's cookie-authenticated endpoints and perform credentialed state-changing requests. This affects applications that enable credentialed CORS without restricting `origin`.

### Summary With `credentials: true` and no explicit `origin` (the default wildcard), the CORS Middleware reflects the request's `Origin` and sends `Access-Control-Allow-Credentials: true`. Any site can then make credentialed cross-origin requests and read the responses, exposing cookie-authenticated endpoints to arbitrary origins. ### Details The spec forbids `Access-Control-Allow-Origin: *` with credentials and browsers reject it, so this configuration used to fail closed. In affected versions the middleware reflects the request `Origin` instead, so it now succeeds for every origin, including `null`. The preflight also echoes the requested headers back, approving non-simple credentialed requests too. This issue arises when an application enables `credentials: true` and leaves `origin` unset or set to the wildcard. ### Impact Any third-party page a logged-in user visits can read the application's cookie-authenticated endpoints and perform credentialed state-changing requests. This affects applications that enable credentialed CORS without restricting `origin`.