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Graph/subdomain-cookie-domain-mismatch

Pattern

Subdomain Cookie Domain Mismatch

subdomain-cookie-domain-mismatch

Cookie domain scope mismatches across backend vs frontend subdomains break authentication state because browsers only send cookies that match the cookie Domain attribute, so apps can’t access expected cookies in JS and sessions silently fail until domain is explicitly set.

Node Details

Public graph metadata

Updated7/29/2026

Connections

30 linked nodes

Cookie “__vercel_live_token” has been rejected because it is in a cross-site context and its “SameSite” is “Lax” or “Strict” — deployed it on Vercel. Tension: But i setup cookies in my project like this. Outcome: Then you need to use https://localhost:5000 and not http://localhost:5000.

When the UI calls the `POST /auth/callback/passkey` endpoint. Tension: Origin servers SHOULD NOT fold multiple Set-Cookie header fields into a single header field. Outcome: Cloudflare seem to be in the wrong here.

when I refresh my page the cookie gets deleted — I have deployed my sveltekit frontend and python flask backend on vercel. Tension: On localhost, they worked just fine however when I deployed it, the cookies were not persistent. Outcome: it does sets the cookie, but on refresh, the cookie gets disappeared.

django.security.csrf: Forbidden (Origin checking failed - https://sentry-domain.com does not match any trusted origins.) — /account/recover/ (status_code=403 request=<WSGIRequest: POST '/account/recover/'>). Tension: when it comes to login (correct or wrong username and password). Outcome: It is solved by some steps.

Using Fetch from my `index.html` from my `portal.mydomain.com` does not. — Enter `api.mydomain.com` into a browser directly does save my cookie. Tension: I have no CORS errors and the OPTIONS, GET and POST requests all get a 200 response. Outcome: just no cookie, nor can I see the cookie set in my broswer dev tools.

RedirectResponse goes to "/" without the authentication cookie

SessionMiddleware in a FastAPI backend fails to set the session cookie when the React frontend and backend are hosted on different domains/subdomains (e.g., XXX-ui.fly.dev vs XXX-api.fly.dev). The browser rejects the cookie with an 'invalid domain' error and no session is maintained.

were not accessible in js and in browser — Cookies are being set and sent with the next request. Outcome: The problem solved by adding `domain="blueberry.adefe.xyz"` to the cookie in response.

MissingKeyMissing Key-Pair-Id query parameter or cookie value — {urn}/manifest/{derivativeurn}/signedcookies. Tension: I get the following error that suggest I'm missing a header.

Executing an authenticated AWS AppSync GraphQL mutation from a Next.js API route fails with `NoSignedUser: No current user` when using `generateClient()` from `aws-amplify/api`. Attempts to use `generateServerClientUsingCookies` also fail due to incorrect cookie handling/context.

the cookie will be specifically set with `domain=app.sunsetland.com.au`. Tension: if we were to host another subdomain aside from `app.`, we actually would likely encounter the reCAPTCHA challenge again.

Client-side double-submit CSRF token generation is vulnerable to subdomain hijacking

Confusion about cookie authentication versus token authentication

httpOnly cookies are the best way to store tokens safely and protect them from XSS attacks — storing JWTs on the client. Tension: JavaScript won't be allowed to read httpOnly cookies. How would the client handle routes authentication? Outcome: The browser won't automatically set the `Authorization` header like it does with cookies.

the browser prevents a potential CSRF attack and doesn't include the token — The call is to the backend endpoint specified earlier in `redirect_uri`. Tension: I need a browser to include the `ASP.NET_SessionId` cookie in the request. Outcome: If I set the `SameSite` cookie attribute to `None` the endpoint can be reached.

The Heroku-hosted MERN app receives many automated-looking requests from the same forwarded IP in the same second, with suspicious query/path content (e.g., unexpected “if”/“php” strings). This behavior appears to be scanning or an attack proxy and raises concerns about security and abuse.

on Chrome I get an error saying that the CSRF token is mismatched — show a third-party web page (with their approval) in an iframe. Tension: This site has a different domain to my parent site. Outcome: The site displays fine on firefox.

If I check 'Remember Me' in form, this add a cookie with name "REMEMBERME". Tension: I'm implementing custom authenticator. Outcome: your cookie is normal.

The session identifier (req.sessionID) changed on every subsequent HTTP request from the React client to the Express server, preventing consistent session persistence.

Accessing https://example.com results in a “too many redirects” loop, while other domain variants redirect correctly for a React app served by Apache with Cloudflare-managed DNS/SSL.

React frontend never sees the authorization code and the code remains undefined

req.cookies.jwt is defined in localhost but undefined in deployment — The cookies are being set in the browser. Tension: the only problem is I can't access them. Outcome: Here to ken is undefined.

After signing in, middleware redirection occurs, but the browser URL remains unchanged (e.g., it doesn't update to the intended callback/protected route).

The browser does not store the refresh token cookie returned by the Django Ninja login endpoint, even though the cookie appears in the response headers and the fetch call uses credentials: 'include'.

one is working without any credential or cookie[SessionId] but another one is not working — two api's in my spring mvc project which have identical structure. Tension: while calling using Postman or while hitting the APIs in browser/UI project.

even when correct username and password is provided, even in that case the control is redirected to login page instead of home page — I was implementing an authentication mechanism for my app.

Requests to the Django/DRF backend fail with “CSRF Failed: Origin checking failed - http://localhost:8000/ does not match any trusted origins.”

Custom GoDaddy domain does not connect correctly to the Railway web app

curl will accept and store the super-cookie — In lib/cookie.c, Curl_cookie_add() guards against setting cookies whose Domain attribute is a Public Suffix. Tension: libpsl's matching is case-sensitive against its lowercase PSL data. Outcome: the PSL test never sees the canonical 'co.uk'.

throws "Cookies can only be modified in a Server Action or Route Handler" — called from Next.js 15 Server Components (pages, layouts). Tension: The error appears intermittently — only when the session needs refreshing (controlled by `updateAge` config). Outcome: With `updateAge: 300` (5 minutes), it crashes every ~5 minutes for active users.

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