diff --git a/app/api/watch/[videoId]/upload-token/route.ts b/app/api/watch/[videoId]/upload-token/route.ts
index 9a12bfc..49f4b62 100644
--- a/app/api/watch/[videoId]/upload-token/route.ts
+++ b/app/api/watch/[videoId]/upload-token/route.ts
@@ -2,6 +2,7 @@ import { NextRequest } from 'next/server';
 import { auth, checkProjectAccess } from '@/lib/auth';
 import { db } from '@/lib/db';
 import { rateLimit } from '@/lib/rate-limit';
+import { isTrustedSameOriginRequest } from '@/lib/request-origin';
 import { validateShareLinkAccess } from '@/lib/share-links';
 import { getShareSessionFromRequest } from '@/lib/share-session';
 import { apiErrors, successResponse, withCacheControl } from '@/lib/api-response';
@@ -20,7 +21,7 @@ function validateSameOriginRequest(request: NextRequest): Response | null {
     return apiErrors.forbidden('Missing Origin header');
   }
 
-  if (origin !== request.nextUrl.origin) {
+  if (!isTrustedSameOriginRequest(request)) {
     return apiErrors.forbidden('Cross-origin requests are not allowed');
   }
 
diff --git a/app/watch/[videoId]/session/route.ts b/app/watch/[videoId]/session/route.ts
index 219cf92..66dbca2 100644
--- a/app/watch/[videoId]/session/route.ts
+++ b/app/watch/[videoId]/session/route.ts
@@ -2,6 +2,7 @@ import { createHash } from 'crypto';
 import { NextRequest, NextResponse } from 'next/server';
 import { db } from '@/lib/db';
 import { checkRateLimit, getClientIp, rateLimit, rateLimitHeaders } from '@/lib/rate-limit';
+import { isTrustedSameOriginRequest } from '@/lib/request-origin';
 import { MAX_SHARE_PASSWORD_LENGTH, validateShareLinkAccess } from '@/lib/share-links';
 import {
   createPendingShareValue,
@@ -38,7 +39,7 @@ function validateSameOriginRequest(request: NextRequest): NextResponse | null {
     return NextResponse.json({ error: 'Missing Origin header' }, { status: 403 });
   }
 
-  if (origin !== request.nextUrl.origin) {
+  if (!isTrustedSameOriginRequest(request)) {
     return NextResponse.json({ error: 'Cross-origin requests are not allowed' }, { status: 403 });
   }
 
diff --git a/lib/request-origin.ts b/lib/request-origin.ts
new file mode 100644
index 0000000..0bff1ff
--- /dev/null
+++ b/lib/request-origin.ts
@@ -0,0 +1,63 @@
+import type { NextRequest } from 'next/server';
+
+function normalizeOrigin(value: string): string | null {
+  try {
+    return new URL(value).origin;
+  } catch {
+    return null;
+  }
+}
+
+function getConfiguredOrigins(): string[] {
+  const configured = [process.env.NEXT_PUBLIC_APP_URL, process.env.NEXTAUTH_URL];
+  return configured
+    .filter((value): value is string => typeof value === 'string' && value.trim().length > 0)
+    .map((value) => normalizeOrigin(/^https?:\/\//i.test(value) ? value : `https://${value}`))
+    .filter((value): value is string => value !== null);
+}
+
+function getForwardedOrigin(request: NextRequest): string | null {
+  const forwardedProto = request.headers.get('x-forwarded-proto')?.split(',')[0]?.trim();
+  const forwardedHost = request.headers.get('x-forwarded-host')?.split(',')[0]?.trim();
+
+  if (!forwardedProto || !forwardedHost) return null;
+  return normalizeOrigin(`${forwardedProto}://${forwardedHost}`);
+}
+
+function getHostHeaderOrigin(request: NextRequest): string | null {
+  const host = request.headers.get('host')?.split(',')[0]?.trim();
+  if (!host) return null;
+
+  const forwardedProto = request.headers.get('x-forwarded-proto')?.split(',')[0]?.trim();
+  const protocol = forwardedProto || request.nextUrl.protocol.replace(':', '');
+  if (!protocol) return null;
+
+  return normalizeOrigin(`${protocol}://${host}`);
+}
+
+export function getAllowedRequestOrigins(request: NextRequest): Set<string> {
+  const origins = new Set<string>();
+  origins.add(request.nextUrl.origin);
+
+  const forwardedOrigin = getForwardedOrigin(request);
+  if (forwardedOrigin) origins.add(forwardedOrigin);
+
+  const hostHeaderOrigin = getHostHeaderOrigin(request);
+  if (hostHeaderOrigin) origins.add(hostHeaderOrigin);
+
+  for (const configuredOrigin of getConfiguredOrigins()) {
+    origins.add(configuredOrigin);
+  }
+
+  return origins;
+}
+
+export function isTrustedSameOriginRequest(request: NextRequest): boolean {
+  const requestOrigin = request.headers.get('origin');
+  if (!requestOrigin) return false;
+
+  const normalizedRequestOrigin = normalizeOrigin(requestOrigin);
+  if (!normalizedRequestOrigin) return false;
+
+  return getAllowedRequestOrigins(request).has(normalizedRequestOrigin);
+}