CVE-2026-90896: Ecommerce Template Auth Bypass Vulnerability

CVE-2026-90896 Overview

CVE-2026-90896 is a Missing Authentication for Critical Function vulnerability [CWE-306] in the MarcosCamara01 Ecommerce Template. The flaw resides in the checkout session lookup handler at src/app/api/stripe/checkout_sessions/route.ts, exposed at GET /api/stripe/checkout_sessions. An unauthenticated remote attacker who obtains a valid Stripe Checkout Session id (prefixed cs_...) can retrieve the full session object. Disclosed data includes the buyer's name, email, phone number, billing address, amount paid, and internal userId. The endpoint calls stripe.checkout.sessions.retrieve() and returns the result without validating authentication or session ownership.

Critical Impact

Any actor holding a leaked cs_... session identifier can read a buyer's personally identifiable information (PII) without authentication.

Affected Products

• MarcosCamara01 Ecommerce Template versions before commit 91e273c
• The src/app/api/stripe/checkout_sessions/route.ts handler
• Deployments exposing GET /api/stripe/checkout_sessions publicly

Discovery Timeline

• 2026-09-14 - CVE-2026-90896 published to NVD
• 2026-09-15 - Last updated in NVD database

Technical Details for CVE-2026-90896

Vulnerability Analysis

The vulnerable handler accepts a session_id query parameter, validates it starts with cs_, and directly calls stripe.checkout.sessions.retrieve(). It returns the entire Stripe Checkout Session object to the caller. The handler performs no identity check and no ownership check tying the requester to the session. Sibling endpoints such as POST /api/stripe/payment already enforced authentication using auth.api.getSession(), making the omission on the GET handler an inconsistent access control decision rather than an architectural constraint.

Root Cause

The root cause is missing authentication and authorization on a data retrieval endpoint that returns sensitive personal data. The handler treats knowledge of the session_id as sufficient authorization, which is a broken access control pattern. Stripe Checkout Session ids are not designed to be secret authenticators.

Attack Vector

The session_id is embedded in the buyer's browser URL after checkout, because success_url is set to /result?session_id={CHECKOUT_SESSION_ID}. This identifier leaks through Referer headers to third-party sites, analytics platforms, server access logs, and shared-machine browser history. An attacker who obtains any such identifier can issue an unauthenticated request to GET /api/stripe/checkout_sessions?session_id=cs_... and receive the buyer's PII.

// Security patch: require auth and ownership on checkout session lookup
 import { z } from "zod";
 
 import { stripe } from "@/lib/stripe";
+import { auth } from "@/utils/auth";
 
 const checkoutSessionQuerySchema = z.object({
   session_id: z.string().startsWith("cs_", "Invalid CheckoutSession ID"),
 });
 
 export async function GET(req: NextRequest) {
   try {
+    const authSession = await auth.api.getSession({ headers: req.headers });
+    if (!authSession?.user?.id) {
+      return NextResponse.json(
+        { statusCode: 401, message: "Unauthorized" },
+        { status: 401 },
+      );
+    }
+
     const parsed = checkoutSessionQuerySchema.safeParse({
       session_id: req.nextUrl.searchParams.get("session_id"),
     });
// Source: [GitHub Commit 91e273c](https://github.com/MarcosCamara01/ecommerce-template/commit/91e273c69d976a3d205179e66e01fc399bfdd08b)

Detection Methods for CVE-2026-90896

Indicators of Compromise

• Unauthenticated GET requests to /api/stripe/checkout_sessions in HTTP access logs.
• Requests to the endpoint from IP addresses or user agents that never completed a checkout flow.
• Bursts of requests iterating different cs_...session_id values from a single source.
• Referer headers in third-party logs containing /result?session_id=cs_... patterns.

Detection Strategies

• Review web server and reverse-proxy logs for GET /api/stripe/checkout_sessions calls lacking an authenticated session cookie or bearer token.
• Correlate application logs with Stripe API calls to identify session retrievals not tied to the owning userId.
• Deploy a Web Application Firewall (WAF) rule that blocks the endpoint when no authenticated session context is present.

Monitoring Recommendations

• Alert on any 200-status response from /api/stripe/checkout_sessions served to an unauthenticated caller.
• Monitor outbound Referer leakage by inspecting third-party analytics and CDN logs for session_id=cs_ query strings.
• Track anomalous access patterns to Stripe-adjacent endpoints, including high request rates and enumeration behavior.

How to Mitigate CVE-2026-90896

Immediate Actions Required

• Update the MarcosCamara01 Ecommerce Template to a build that includes commit 91e273c or later.
• Rotate any exposed Stripe session identifiers and audit access logs for prior unauthenticated retrievals.
• Change the success_url to avoid placing the session_id in the browser URL, or replace it with a short-lived server-side token.

Patch Information

The fix is delivered in commit 91e273c of the MarcosCamara01 Ecommerce Template repository. The patch adds auth.api.getSession({ headers: req.headers }) at the top of the GET handler and returns HTTP 401 when no authenticated user is present. Deployments must additionally enforce ownership by comparing the session's client_reference_id or metadata userId against authSession.user.id. See the GitHub commit and the CVE-2026-90896 security analysis for details.

Workarounds

• Place the /api/stripe/checkout_sessions route behind reverse-proxy authentication until the patch is deployed.
• Strip the session_id from the client-facing URL and pass a signed, short-lived token instead.
• Set Referrer-Policy: no-referrer on the success page to reduce leakage of cs_... identifiers to third parties.

# Nginx example: require an authenticated session cookie on the vulnerable route
location = /api/stripe/checkout_sessions {
    if ($cookie_session = "") {
        return 401;
    }
    proxy_pass http://app_backend;
}