hono: CORS Middleware reflects any Origin with credentials when `origin` defaults to the wildcard

### 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`.

Source published

16 Jun 2026 14:15:39 UTC

Source modified

10 Sep 2026 03:50:48 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N

Publisher rating · HIGH