diff --git a/services/mam-api/src/routes/auth.js b/services/mam-api/src/routes/auth.js
index 54d3e4c..07578b9 100644
--- a/services/mam-api/src/routes/auth.js
+++ b/services/mam-api/src/routes/auth.js
@@ -12,6 +12,78 @@ import pool from '../db/pool.js';
 
 const router = express.Router();
 
+// ---------------------------------------------------------------------------
+// BUG FIX #6: In-memory login rate limiter.
+//
+// Brute-force protection for POST /login. Tracks failed attempts per
+// (IP, username) pair; after MAX_ATTEMPTS failures within WINDOW_MS the
+// endpoint returns 429 for LOCKOUT_MS regardless of the password supplied.
+//
+// This is intentionally simple — no Redis dependency, no persistent state
+// across restarts. For a production deployment behind a load balancer, use
+// express-rate-limit with a Redis store or a dedicated WAF rule instead.
+// ---------------------------------------------------------------------------
+const MAX_ATTEMPTS  = parseInt(process.env.LOGIN_MAX_ATTEMPTS  || '10', 10);
+const WINDOW_MS     = parseInt(process.env.LOGIN_WINDOW_MS     || String(15 * 60 * 1000), 10);  // 15 min
+const LOCKOUT_MS    = parseInt(process.env.LOGIN_LOCKOUT_MS    || String(15 * 60 * 1000), 10);  // 15 min
+
+// Map key → { attempts: number, lockedUntil: number | null, firstAttempt: number }
+const loginAttempts = new Map();
+
+// Housekeeping: prune expired entries every 10 min so the Map doesn't grow
+// unboundedly on high-traffic or attack traffic.
+setInterval(() => {
+  const now = Date.now();
+  for (const [key, entry] of loginAttempts.entries()) {
+    const expired = entry.lockedUntil
+      ? now > entry.lockedUntil
+      : now - entry.firstAttempt > WINDOW_MS;
+    if (expired) loginAttempts.delete(key);
+  }
+}, 10 * 60 * 1000).unref();
+
+function getAttemptKey(req, username) {
+  // Use the real client IP (trust proxy headers set by nginx/load-balancer)
+  const ip = req.ip || req.socket.remoteAddress || 'unknown';
+  return `${ip}:${(username || '').trim().toLowerCase()}`;
+}
+
+function checkRateLimit(req, username) {
+  const key = getAttemptKey(req, username);
+  const now = Date.now();
+  const entry = loginAttempts.get(key);
+
+  if (entry) {
+    // Still locked out?
+    if (entry.lockedUntil && now < entry.lockedUntil) {
+      const retryAfterSec = Math.ceil((entry.lockedUntil - now) / 1000);
+      return { limited: true, retryAfterSec };
+    }
+    // Window expired — reset
+    if (now - entry.firstAttempt > WINDOW_MS) {
+      loginAttempts.delete(key);
+    }
+  }
+  return { limited: false };
+}
+
+function recordFailedAttempt(req, username) {
+  const key = getAttemptKey(req, username);
+  const now = Date.now();
+  const entry = loginAttempts.get(key) || { attempts: 0, lockedUntil: null, firstAttempt: now };
+
+  // Don't update firstAttempt if there's an existing entry within the window
+  entry.attempts += 1;
+  if (entry.attempts >= MAX_ATTEMPTS) {
+    entry.lockedUntil = now + LOCKOUT_MS;
+  }
+  loginAttempts.set(key, entry);
+}
+
+function clearAttempts(req, username) {
+  loginAttempts.delete(getAttemptKey(req, username));
+}
+
 // ---------------------------------------------------------------------------
 // POST /login
 // ---------------------------------------------------------------------------
@@ -23,6 +95,15 @@ router.post('/login', async (req, res, next) => {
       return res.status(400).json({ error: 'Username and password are required' });
     }
 
+    // BUG FIX #6: Check rate limit before hitting the DB or bcrypt.
+    const rateCheck = checkRateLimit(req, username);
+    if (rateCheck.limited) {
+      res.set('Retry-After', String(rateCheck.retryAfterSec));
+      return res.status(429).json({
+        error: `Too many failed login attempts. Try again in ${rateCheck.retryAfterSec} seconds.`,
+      });
+    }
+
     const result = await pool.query(
       'SELECT * FROM users WHERE username = $1',
       [username.trim().toLowerCase()]
@@ -31,6 +112,7 @@ router.post('/login', async (req, res, next) => {
     if (result.rows.length === 0) {
       // Timing-safe: still run compare on a dummy hash so response time is constant
       await bcrypt.compare(password, '$2b$12$invalidhashpadding000000000000000000000000000000000000');
+      recordFailedAttempt(req, username);
       return res.status(401).json({ error: 'Invalid credentials' });
     }
 
@@ -38,9 +120,13 @@ router.post('/login', async (req, res, next) => {
     const valid = await bcrypt.compare(password, user.password_hash);
 
     if (!valid) {
+      recordFailedAttempt(req, username);
       return res.status(401).json({ error: 'Invalid credentials' });
     }
 
+    // Successful login — clear any accumulated failed attempts
+    clearAttempts(req, username);
+
     // Regenerate session ID to prevent fixation attacks
     req.session.regenerate((err) => {
       if (err) return next(err);