diff --git a/src/app/api/providers/route.ts b/src/app/api/providers/route.ts
index 877b3dbde3..e732508444 100644
--- a/src/app/api/providers/route.ts
+++ b/src/app/api/providers/route.ts
@@ -32,7 +32,10 @@ import {
 import { requireManagementAuth } from "@/lib/api/requireManagementAuth";
 import { isManagedProviderConnectionId } from "@/lib/providers/catalog";
 import { isApiKeyRevealEnabled, maskStoredApiKey } from "@/lib/apiKeyExposure";
-import { buildModelSyncInternalHeaders } from "@/shared/services/modelSyncScheduler";
+import {
+  buildModelSyncInternalHeaders,
+  getModelSyncInternalBaseUrl,
+} from "@/shared/services/modelSyncScheduler";
 
 // GET /api/providers - List all connections
 export async function GET(request: Request) {
@@ -174,7 +177,12 @@ export async function POST(request: Request) {
     // auth header (defense in depth) and an X-Internal-Auto-Sync marker for
     // log correlation.
     try {
-      const internalOrigin = new URL(request.url).origin;
+      // SECURITY: use the trusted loopback/env-pinned origin, NOT
+      // `new URL(request.url).origin` — the latter comes from the client-
+      // controlled Host header, which would let a caller redirect this
+      // credential-bearing internal self-fetch to an arbitrary host
+      // (SSRF + internal-auth-header exfiltration; CodeQL js/request-forgery).
+      const internalOrigin = getModelSyncInternalBaseUrl();
       const cookieHeader = request.headers.get("cookie") || "";
       const syncHeaders: Record<string, string> = {
         "Content-Type": "application/json",
diff --git a/src/shared/services/modelSyncScheduler.ts b/src/shared/services/modelSyncScheduler.ts
index fe9478cdb6..553a6783e1 100644
--- a/src/shared/services/modelSyncScheduler.ts
+++ b/src/shared/services/modelSyncScheduler.ts
@@ -24,6 +24,19 @@ const INTERNAL_BASE_URL =
   process.env.NEXT_PUBLIC_APP_URL ||
   `http://127.0.0.1:${dashboardPort}`;
 
+/**
+ * Trusted origin for server-internal self-fetches (model sync, auto-discovery).
+ *
+ * SECURITY: never derive this from the incoming request (`request.url` /
+ * `Host` header) — that is client-controlled and lets a caller redirect an
+ * internal, credential-bearing self-fetch to an arbitrary host (SSRF +
+ * internal-auth-header exfiltration; CodeQL js/request-forgery). Always use
+ * this loopback/env-pinned origin instead.
+ */
+export function getModelSyncInternalBaseUrl(): string {
+  return INTERNAL_BASE_URL;
+}
+
 const globalState = globalThis as typeof globalThis & {
   __omnirouteModelSyncInternalAuthToken?: string;
 };
diff --git a/tests/unit/providers-autosync-ssrf-323.test.ts b/tests/unit/providers-autosync-ssrf-323.test.ts
new file mode 100644
index 0000000000..1df4c4dcf2
--- /dev/null
+++ b/tests/unit/providers-autosync-ssrf-323.test.ts
@@ -0,0 +1,35 @@
+/**
+ * Regression guard — CodeQL js/request-forgery alert #323 (v3.8.13).
+ *
+ * POST /api/providers fires a non-blocking self-fetch to the connection's
+ * /sync-models route, forwarding the management cookie + internal sync auth
+ * headers. #3267 built that self-fetch origin from `new URL(request.url).origin`
+ * — i.e. the client-controlled Host header — so a caller could redirect the
+ * credential-bearing internal request to an arbitrary host (SSRF + internal
+ * auth-header exfiltration).
+ *
+ * The origin must come from the trusted loopback/env-pinned base URL
+ * (`getModelSyncInternalBaseUrl()`), never from the incoming request.
+ */
+
+import test from "node:test";
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { join } from "node:path";
+
+const routeSrc = readFileSync(
+  join(import.meta.dirname, "../../src/app/api/providers/route.ts"),
+  "utf8"
+);
+
+test("POST /api/providers auto-sync uses the trusted internal origin (not request.url) — #323", () => {
+  assert.ok(
+    routeSrc.includes("getModelSyncInternalBaseUrl()"),
+    "auto-sync self-fetch must derive its origin from getModelSyncInternalBaseUrl()"
+  );
+  assert.doesNotMatch(
+    routeSrc,
+    /const\s+internalOrigin\s*=\s*new URL\(request\.url\)\.origin/,
+    "auto-sync origin must NOT be derived from the client-controlled request.url/Host (SSRF, CodeQL js/request-forgery #323)"
+  );
+});