diff --git a/docker/nginx-https.conf b/docker/nginx-https.conf
index d2e38f5b..668df97c 100644
--- a/docker/nginx-https.conf
+++ b/docker/nginx-https.conf
@@ -433,8 +433,8 @@ http {
             proxy_set_header X-Real-IP $remote_addr;
             proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
             proxy_set_header X-Forwarded-Proto $proxy_x_forwarded_proto;
-            proxy_set_header X-Forwarded-Port $server_port;
-            proxy_set_header X-Forwarded-Host $http_host;
+            proxy_set_header X-Forwarded-Port $proxy_x_forwarded_port;
+            proxy_set_header X-Forwarded-Host $proxy_x_forwarded_host;
 
             proxy_read_timeout 86400s;
             proxy_send_timeout 86400s;
@@ -676,8 +676,8 @@ http {
             proxy_set_header X-Real-IP $remote_addr;
             proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
             proxy_set_header X-Forwarded-Proto $proxy_x_forwarded_proto;
-            proxy_set_header X-Forwarded-Port $server_port;
-            proxy_set_header X-Forwarded-Host $http_host;
+            proxy_set_header X-Forwarded-Port $proxy_x_forwarded_port;
+            proxy_set_header X-Forwarded-Host $proxy_x_forwarded_host;
 
             proxy_read_timeout 86400s;
             proxy_send_timeout 86400s;
diff --git a/docker/nginx.conf b/docker/nginx.conf
index a8a44e2a..68cff5a6 100644
--- a/docker/nginx.conf
+++ b/docker/nginx.conf
@@ -434,8 +434,8 @@ http {
             proxy_set_header X-Real-IP $remote_addr;
             proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
             proxy_set_header X-Forwarded-Proto $proxy_x_forwarded_proto;
-            proxy_set_header X-Forwarded-Port $server_port;
-            proxy_set_header X-Forwarded-Host $http_host;
+            proxy_set_header X-Forwarded-Port $proxy_x_forwarded_port;
+            proxy_set_header X-Forwarded-Host $proxy_x_forwarded_host;
 
             proxy_read_timeout 86400s;
             proxy_send_timeout 86400s;
@@ -677,8 +677,8 @@ http {
             proxy_set_header X-Real-IP $remote_addr;
             proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
             proxy_set_header X-Forwarded-Proto $proxy_x_forwarded_proto;
-            proxy_set_header X-Forwarded-Port $server_port;
-            proxy_set_header X-Forwarded-Host $http_host;
+            proxy_set_header X-Forwarded-Port $proxy_x_forwarded_port;
+            proxy_set_header X-Forwarded-Host $proxy_x_forwarded_host;
 
             proxy_read_timeout 86400s;
             proxy_send_timeout 86400s;
diff --git a/src/backend/utils/request-origin.test.ts b/src/backend/utils/request-origin.test.ts
index d569f6e9..711de73a 100644
--- a/src/backend/utils/request-origin.test.ts
+++ b/src/backend/utils/request-origin.test.ts
@@ -3,6 +3,7 @@ import {
   getRequestBasePath,
   getRequestBaseUrl,
   getRequestBaseUrlWithForceHTTPS,
+  getRequestOrigin,
   normalizeBasePath,
 } from "./request-origin.js";
 
@@ -106,3 +107,52 @@ describe("getRequestBasePath", () => {
     ).toBe("https://example.com/termix");
   });
 });
+
+describe("getRequestOrigin", () => {
+  it("ignores non-numeric forwarded ports", () => {
+    expect(
+      getRequestOrigin(
+        request({
+          "x-forwarded-proto": "https",
+          "x-forwarded-host": "termix.test.de",
+          "x-forwarded-port": "{server_port}",
+        }),
+      ),
+    ).toBe("https://termix.test.de");
+  });
+
+  it("drops invalid ports embedded in forwarded hosts", () => {
+    expect(
+      getRequestOrigin(
+        request({
+          "x-forwarded-proto": "https",
+          "x-forwarded-host": "termix.test.de:{server_port}",
+        }),
+      ),
+    ).toBe("https://termix.test.de");
+  });
+
+  it("keeps valid non-default forwarded ports", () => {
+    expect(
+      getRequestOrigin(
+        request({
+          "x-forwarded-proto": "https",
+          "x-forwarded-host": "termix.test.de",
+          "x-forwarded-port": "8443",
+        }),
+      ),
+    ).toBe("https://termix.test.de:8443");
+  });
+
+  it("omits default forwarded ports", () => {
+    expect(
+      getRequestOrigin(
+        request({
+          "x-forwarded-proto": "https",
+          "x-forwarded-host": "termix.test.de",
+          "x-forwarded-port": "443",
+        }),
+      ),
+    ).toBe("https://termix.test.de");
+  });
+});
diff --git a/src/backend/utils/request-origin.ts b/src/backend/utils/request-origin.ts
index 1f91d1cf..7ecf54eb 100644
--- a/src/backend/utils/request-origin.ts
+++ b/src/backend/utils/request-origin.ts
@@ -7,6 +7,44 @@ function firstHeaderValue(value: string | string[] | undefined): string {
   return raw.split(",")[0].trim();
 }
 
+function normalizePort(value: string | string[] | undefined): string {
+  const raw = firstHeaderValue(value);
+  if (!/^\d+$/.test(raw)) return "";
+
+  const port = Number(raw);
+  if (!Number.isInteger(port) || port < 1 || port > 65535) return "";
+
+  return String(port);
+}
+
+function splitHostHeader(value: string | string[] | undefined): {
+  host: string;
+  port: string;
+} {
+  const raw = firstHeaderValue(value) || "localhost";
+
+  if (raw.startsWith("[")) {
+    const match = raw.match(/^(\[[^\]]+\])(?::(.+))?$/);
+    return {
+      host: match?.[1] || raw,
+      port: normalizePort(match?.[2]),
+    };
+  }
+
+  const parts = raw.split(":");
+  if (parts.length === 2) {
+    return {
+      host: parts[0] || "localhost",
+      port: normalizePort(parts[1]),
+    };
+  }
+
+  return {
+    host: raw,
+    port: "",
+  };
+}
+
 export function normalizeBasePath(value: unknown): string {
   if (typeof value !== "string") return "";
   let basePath = value.split(",")[0].trim();
@@ -45,38 +83,23 @@ export function getRequestOrigin(req: Request | IncomingMessage): string {
       : "http";
   }
 
-  const portHeader = req.headers["x-forwarded-port"];
-  let port: string | undefined =
-    typeof portHeader === "string"
-      ? portHeader.split(",")[0].trim()
-      : undefined;
+  let port = normalizePort(req.headers["x-forwarded-port"]);
+  const { host, port: hostPort } = splitHostHeader(
+    req.headers["x-forwarded-host"] || req.headers.host,
+  );
+  port ||= hostPort;
 
-  const hostHeaderRaw =
-    req.headers["x-forwarded-host"] || req.headers.host || "localhost";
-  const hostHeader =
-    typeof hostHeaderRaw === "string"
-      ? hostHeaderRaw.split(",")[0].trim()
-      : String(hostHeaderRaw);
-
-  if (!port && hostHeader.includes(":")) {
-    const parts = hostHeader.split(":");
-    if (parts.length === 2 && !parts[0].includes("[")) {
-      port = parts[1];
-    }
-  }
-
-  const hostWithoutPort = hostHeader.split(":")[0];
   if (port) {
     const isDefaultPort =
       (protocol === "http" && port === "80") ||
       (protocol === "https" && port === "443");
 
     return isDefaultPort
-      ? `${protocol}://${hostWithoutPort}`
-      : `${protocol}://${hostWithoutPort}:${port}`;
+      ? `${protocol}://${host}`
+      : `${protocol}://${host}:${port}`;
   }
 
-  return `${protocol}://${hostWithoutPort}`;
+  return `${protocol}://${host}`;
 }
 
 export function getRequestOriginWithForceHTTPS(