diff --git a/paperless-backend/src/auth/api-keys.controller.spec.ts b/paperless-backend/src/auth/api-keys.controller.spec.ts
new file mode 100644
index 0000000..80fe10f
--- /dev/null
+++ b/paperless-backend/src/auth/api-keys.controller.spec.ts
@@ -0,0 +1,13 @@
+import { PERMISSIONS_KEY } from './permissions.decorator';
+import { Permission } from './permissions.enum';
+import { ApiKeysController } from './api-keys.controller';
+
+describe('ApiKeysController', () => {
+  it('verlangt MANAGE_SETTINGS – sonst kann sich jeder OIDC-Benutzer einen API-Key erzeugen', () => {
+    const required: unknown = Reflect.getMetadata(
+      PERMISSIONS_KEY,
+      ApiKeysController,
+    );
+    expect(required).toEqual([Permission.MANAGE_SETTINGS]);
+  });
+});
diff --git a/paperless-backend/src/auth/api-keys.controller.ts b/paperless-backend/src/auth/api-keys.controller.ts
index 4d6cc36..cf79e90 100644
--- a/paperless-backend/src/auth/api-keys.controller.ts
+++ b/paperless-backend/src/auth/api-keys.controller.ts
@@ -9,9 +9,14 @@ import {
 } from '@nestjs/common';
 import { ApiKeysService } from './api-keys.service';
 import { JwtAuthGuard } from './jwt-auth.guard';
+import { RequirePermissions } from './permissions.decorator';
+import { Permission } from './permissions.enum';
 
 @Controller('api/api-keys')
 @UseGuards(JwtAuthGuard)
+// Ein API-Key umgeht im PermissionsGuard jede Rechteprüfung – Anlegen und
+// Verwalten darf daher nur, wer ohnehin alle Einstellungen verwalten darf.
+@RequirePermissions(Permission.MANAGE_SETTINGS)
 export class ApiKeysController {
   constructor(private readonly apiKeysService: ApiKeysService) {}
 
diff --git a/paperless-backend/src/inbox/inbox.controller.ts b/paperless-backend/src/inbox/inbox.controller.ts
index 453cc99..6360e58 100644
--- a/paperless-backend/src/inbox/inbox.controller.ts
+++ b/paperless-backend/src/inbox/inbox.controller.ts
@@ -27,6 +27,7 @@ import {
   kennzahlenAusPdf,
   type VergleichKennzahlen,
 } from '../paperless/vergleich-kennzahlen.util';
+import { parseSendEmailBody } from './send-email-body.util';
 
 @Controller('api/inbox')
 @RequirePermissions(Permission.VIEW_SCANNER)
@@ -284,17 +285,10 @@ export class InboxController {
   @HttpCode(204)
   async sendEmail(
     @Param('id') id: string,
-    @Body()
-    body: {
-      to: string;
-      subject: string;
-      body: string;
-      html?: string;
-      segments: { pages: number[]; filename: string }[];
-      sender?: string;
-    },
+    @Body() rawBody: unknown,
     @Request() req: any,
   ): Promise<void> {
+    const body = parseSendEmailBody(rawBody);
     const preferredUsername: string | null =
       req.user?.preferredUsername ?? null;
     const smtpOverride =
diff --git a/paperless-backend/src/inbox/send-email-body.util.spec.ts b/paperless-backend/src/inbox/send-email-body.util.spec.ts
new file mode 100644
index 0000000..a644a4e
--- /dev/null
+++ b/paperless-backend/src/inbox/send-email-body.util.spec.ts
@@ -0,0 +1,50 @@
+import { BadRequestException } from '@nestjs/common';
+import { parseSendEmailBody } from './send-email-body.util';
+
+describe('parseSendEmailBody', () => {
+  const gueltig = {
+    to: 'a@example.org',
+    subject: 'Betreff',
+    body: 'Text',
+    html: '<p>Text</p>',
+    segments: [{ pages: [1, 2], filename: 'beleg' }],
+    sender: 'user',
+  };
+
+  it('übernimmt einen gültigen Body', () => {
+    expect(parseSendEmailBody(gueltig)).toEqual(gueltig);
+  });
+
+  it('lässt html und sender weg, wenn sie fehlen', () => {
+    const ohne = { ...gueltig, html: undefined, sender: undefined };
+    expect(parseSendEmailBody(ohne)).toEqual({
+      to: gueltig.to,
+      subject: gueltig.subject,
+      body: gueltig.body,
+      segments: gueltig.segments,
+    });
+  });
+
+  it.each([
+    ['html als Objekt mit path', { html: { path: '/proc/self/environ' } }],
+    ['body als Objekt mit href', { body: { href: 'http://169.254.169.254/' } }],
+    ['to als Objekt', { to: { address: 'a@example.org' } }],
+    ['to als Array', { to: ['a@example.org'] }],
+    ['subject fehlt', { subject: undefined }],
+    ['segments kein Array', { segments: 'x' }],
+    ['Seite keine Zahl', { segments: [{ pages: ['1'], filename: 'x' }] }],
+    [
+      'filename kein String',
+      { segments: [{ pages: [1], filename: { path: '/etc/passwd' } }] },
+    ],
+    ['sender kein String', { sender: { x: 1 } }],
+  ])('lehnt ab: %s', (_name, patch) => {
+    expect(() => parseSendEmailBody({ ...gueltig, ...patch })).toThrow(
+      BadRequestException,
+    );
+  });
+
+  it('lehnt einen fehlenden Body ab', () => {
+    expect(() => parseSendEmailBody(undefined)).toThrow(BadRequestException);
+  });
+});
diff --git a/paperless-backend/src/inbox/send-email-body.util.ts b/paperless-backend/src/inbox/send-email-body.util.ts
new file mode 100644
index 0000000..da3ece8
--- /dev/null
+++ b/paperless-backend/src/inbox/send-email-body.util.ts
@@ -0,0 +1,66 @@
+import { BadRequestException } from '@nestjs/common';
+
+export interface SendEmailBody {
+  to: string;
+  subject: string;
+  body: string;
+  html?: string;
+  segments: { pages: number[]; filename: string }[];
+  sender?: string;
+}
+
+/**
+ * Prüft den Body von `POST inbox/:id/send-email` streng auf Strings bzw. Zahlen.
+ * Ohne diese Prüfung landen Objekte wie `{ path: '/proc/self/environ' }` direkt
+ * bei nodemailer, das sie als Datei- bzw. URL-Quelle interpretiert.
+ */
+export function parseSendEmailBody(raw: unknown): SendEmailBody {
+  if (!isObject(raw)) throw new BadRequestException('Ungültiger Request-Body');
+  const { to, subject, body, html, segments, sender } = raw;
+
+  for (const [name, wert] of [
+    ['to', to],
+    ['subject', subject],
+    ['body', body],
+  ] as const) {
+    if (typeof wert !== 'string') {
+      throw new BadRequestException(`"${name}" muss ein Text sein`);
+    }
+  }
+  if (html !== undefined && typeof html !== 'string') {
+    throw new BadRequestException('"html" muss ein Text sein');
+  }
+  if (sender !== undefined && typeof sender !== 'string') {
+    throw new BadRequestException('"sender" muss ein Text sein');
+  }
+  if (!Array.isArray(segments)) {
+    throw new BadRequestException('"segments" muss eine Liste sein');
+  }
+  const geprueft = segments.map((seg) => {
+    if (
+      !isObject(seg) ||
+      typeof seg.filename !== 'string' ||
+      !Array.isArray(seg.pages) ||
+      !seg.pages.every((p) => Number.isInteger(p))
+    ) {
+      throw new BadRequestException(
+        'Jedes Segment braucht "filename" (Text) und "pages" (ganze Zahlen)',
+      );
+    }
+    return { pages: seg.pages as number[], filename: seg.filename };
+  });
+
+  const ergebnis: SendEmailBody = {
+    to: to as string,
+    subject: subject as string,
+    body: body as string,
+    segments: geprueft,
+  };
+  if (html !== undefined) ergebnis.html = html;
+  if (sender !== undefined) ergebnis.sender = sender;
+  return ergebnis;
+}
+
+function isObject(v: unknown): v is Record<string, unknown> {
+  return typeof v === 'object' && v !== null && !Array.isArray(v);
+}
diff --git a/paperless-backend/src/postprocessing/mail.service.spec.ts b/paperless-backend/src/postprocessing/mail.service.spec.ts
new file mode 100644
index 0000000..bd27ca8
--- /dev/null
+++ b/paperless-backend/src/postprocessing/mail.service.spec.ts
@@ -0,0 +1,51 @@
+import { ConfigService } from '@nestjs/config';
+import * as nodemailer from 'nodemailer';
+import { MailService } from './mail.service';
+
+jest.mock('nodemailer');
+
+describe('MailService', () => {
+  const sendMail = jest.fn().mockResolvedValue({
+    messageId: 'x',
+    accepted: [],
+    rejected: [],
+    response: 'ok',
+  });
+
+  beforeEach(() => {
+    sendMail.mockClear();
+    (nodemailer.createTransport as jest.Mock).mockReturnValue({ sendMail });
+  });
+
+  const config = {
+    get: (_k: string, d?: unknown) => d,
+  } as unknown as ConfigService;
+
+  it.each([false, true])(
+    'verbietet nodemailer Datei- und URL-Zugriffe (smtpOverride=%s)',
+    async (override) => {
+      const service = new MailService(config);
+      await service.sendMail({
+        to: 'a@example.org',
+        subject: 's',
+        body: 'b',
+        smtpOverride: override
+          ? {
+              host: 'h',
+              port: 25,
+              secure: false,
+              user: 'u',
+              pass: 'p',
+              from: 'f',
+            }
+          : undefined,
+      });
+      expect(sendMail).toHaveBeenCalledWith(
+        expect.objectContaining({
+          disableFileAccess: true,
+          disableUrlAccess: true,
+        }),
+      );
+    },
+  );
+});
diff --git a/paperless-backend/src/postprocessing/mail.service.ts b/paperless-backend/src/postprocessing/mail.service.ts
index e2c27be..d748077 100644
--- a/paperless-backend/src/postprocessing/mail.service.ts
+++ b/paperless-backend/src/postprocessing/mail.service.ts
@@ -69,6 +69,10 @@ export class MailService {
         filename: a.filename,
         content: a.content,
       })),
+      // Inhalte kommen teils vom Aufrufer: nodemailer darf nie Dateien vom
+      // Server lesen oder URLs abrufen (`{ path }` / `{ href }`).
+      disableFileAccess: true,
+      disableUrlAccess: true,
     });
 
     this.logger.log(