diff --git a/frontend/src/App.tsx b/frontend/src/App.tsx
index 0a6f583..995f167 100644
--- a/frontend/src/App.tsx
+++ b/frontend/src/App.tsx
@@ -1,22 +1,41 @@
-import { Routes, Route } from 'react-router-dom';
-import { AuthProvider } from './contexts/AuthContext';
+import { Routes, Route, Navigate, useLocation } from 'react-router-dom';
+import { AuthProvider, useAuth } from './contexts/AuthContext';
 import Layout from './components/Layout';
 import Home from './pages/Home';
 import ProjectPage from './pages/ProjectPage';
 import PackagePage from './pages/PackagePage';
 import Dashboard from './pages/Dashboard';
 import LoginPage from './pages/LoginPage';
+import ChangePasswordPage from './pages/ChangePasswordPage';
 import APIKeysPage from './pages/APIKeysPage';
 import AdminUsersPage from './pages/AdminUsersPage';
 
-function App() {
+// Component that checks if user must change password
+function RequirePasswordChange({ children }: { children: React.ReactNode }) {
+  const { user, loading } = useAuth();
+  const location = useLocation();
+
+  if (loading) {
+    return null;
+  }
+
+  // If user is logged in and must change password, redirect to change password page
+  if (user?.must_change_password && location.pathname !== '/change-password') {
+    return <Navigate to="/change-password" replace />;
+  }
+
+  return <>{children}</>;
+}
+
+function AppRoutes() {
   return (
-    <AuthProvider>
-      <Routes>
-        <Route path="/login" element={<LoginPage />} />
-        <Route
-          path="*"
-          element={
+    <Routes>
+      <Route path="/login" element={<LoginPage />} />
+      <Route path="/change-password" element={<ChangePasswordPage />} />
+      <Route
+        path="*"
+        element={
+          <RequirePasswordChange>
             <Layout>
               <Routes>
                 <Route path="/" element={<Home />} />
@@ -27,9 +46,17 @@ function App() {
                 <Route path="/project/:projectName/:packageName" element={<PackagePage />} />
               </Routes>
             </Layout>
-          }
-        />
-      </Routes>
+          </RequirePasswordChange>
+        }
+      />
+    </Routes>
+  );
+}
+
+function App() {
+  return (
+    <AuthProvider>
+      <AppRoutes />
     </AuthProvider>
   );
 }
diff --git a/frontend/src/api.ts b/frontend/src/api.ts
index f9adafe..0a417a2 100644
--- a/frontend/src/api.ts
+++ b/frontend/src/api.ts
@@ -33,10 +33,43 @@ import {
 
 const API_BASE = '/api/v1';
 
+// Custom error classes for better error handling
+export class ApiError extends Error {
+  status: number;
+
+  constructor(message: string, status: number) {
+    super(message);
+    this.name = 'ApiError';
+    this.status = status;
+  }
+}
+
+export class UnauthorizedError extends ApiError {
+  constructor(message: string = 'Not authenticated') {
+    super(message, 401);
+    this.name = 'UnauthorizedError';
+  }
+}
+
+export class ForbiddenError extends ApiError {
+  constructor(message: string = 'Access denied') {
+    super(message, 403);
+    this.name = 'ForbiddenError';
+  }
+}
+
 async function handleResponse<T>(response: Response): Promise<T> {
   if (!response.ok) {
     const error = await response.json().catch(() => ({ detail: 'Unknown error' }));
-    throw new Error(error.detail || `HTTP ${response.status}`);
+    const message = error.detail || `HTTP ${response.status}`;
+
+    if (response.status === 401) {
+      throw new UnauthorizedError(message);
+    }
+    if (response.status === 403) {
+      throw new ForbiddenError(message);
+    }
+    throw new ApiError(message, response.status);
   }
   return response.json();
 }
@@ -74,6 +107,19 @@ export async function logout(): Promise<void> {
   }
 }
 
+export async function changePassword(currentPassword: string, newPassword: string): Promise<void> {
+  const response = await fetch(`${API_BASE}/auth/change-password`, {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify({ current_password: currentPassword, new_password: newPassword }),
+    credentials: 'include',
+  });
+  if (!response.ok) {
+    const error = await response.json().catch(() => ({ detail: 'Unknown error' }));
+    throw new Error(error.detail || `HTTP ${response.status}`);
+  }
+}
+
 export async function getCurrentUser(): Promise<User | null> {
   try {
     const response = await fetch(`${API_BASE}/auth/me`, {
diff --git a/frontend/src/contexts/AuthContext.tsx b/frontend/src/contexts/AuthContext.tsx
index fe2ae30..b63c4f6 100644
--- a/frontend/src/contexts/AuthContext.tsx
+++ b/frontend/src/contexts/AuthContext.tsx
@@ -8,6 +8,7 @@ interface AuthContextType {
   error: string | null;
   login: (username: string, password: string) => Promise<void>;
   logout: () => Promise<void>;
+  refreshUser: () => Promise<void>;
   clearError: () => void;
 }
 
@@ -71,8 +72,17 @@ export function AuthProvider({ children }: AuthProviderProps) {
     setError(null);
   }, []);
 
+  const refreshUser = useCallback(async () => {
+    try {
+      const currentUser = await getCurrentUser();
+      setUser(currentUser);
+    } catch {
+      setUser(null);
+    }
+  }, []);
+
   return (
-    <AuthContext.Provider value={{ user, loading, error, login, logout, clearError }}>
+    <AuthContext.Provider value={{ user, loading, error, login, logout, refreshUser, clearError }}>
       {children}
     </AuthContext.Provider>
   );
diff --git a/frontend/src/pages/ChangePasswordPage.tsx b/frontend/src/pages/ChangePasswordPage.tsx
new file mode 100644
index 0000000..3d97953
--- /dev/null
+++ b/frontend/src/pages/ChangePasswordPage.tsx
@@ -0,0 +1,156 @@
+import { useState } from 'react';
+import { useNavigate } from 'react-router-dom';
+import { useAuth } from '../contexts/AuthContext';
+import { changePassword } from '../api';
+import './LoginPage.css';
+
+function ChangePasswordPage() {
+  const [currentPassword, setCurrentPassword] = useState('');
+  const [newPassword, setNewPassword] = useState('');
+  const [confirmPassword, setConfirmPassword] = useState('');
+  const [isSubmitting, setIsSubmitting] = useState(false);
+  const [error, setError] = useState<string | null>(null);
+
+  const { user, refreshUser } = useAuth();
+  const navigate = useNavigate();
+
+  async function handleSubmit(e: React.FormEvent) {
+    e.preventDefault();
+
+    if (!currentPassword || !newPassword || !confirmPassword) {
+      setError('Please fill in all fields');
+      return;
+    }
+
+    if (newPassword !== confirmPassword) {
+      setError('New passwords do not match');
+      return;
+    }
+
+    if (newPassword.length < 8) {
+      setError('New password must be at least 8 characters');
+      return;
+    }
+
+    if (newPassword === currentPassword) {
+      setError('New password must be different from current password');
+      return;
+    }
+
+    setIsSubmitting(true);
+    setError(null);
+
+    try {
+      await changePassword(currentPassword, newPassword);
+      // Refresh user to clear must_change_password flag
+      await refreshUser();
+      navigate('/', { replace: true });
+    } catch (err) {
+      setError(err instanceof Error ? err.message : 'Failed to change password');
+    } finally {
+      setIsSubmitting(false);
+    }
+  }
+
+  return (
+    <div className="login-page">
+      <div className="login-container">
+        <div className="login-card">
+          <div className="login-header">
+            <div className="login-logo">
+              <svg width="48" height="48" viewBox="0 0 24 24" fill="none" xmlns="http://www.w3.org/2000/svg">
+                <path d="M6 14 Q6 8 3 8 Q6 4 6 4 Q6 4 9 8 Q6 8 6 14" fill="currentColor" opacity="0.6"/>
+                <rect x="5.25" y="13" width="1.5" height="4" fill="currentColor" opacity="0.6"/>
+                <path d="M12 12 Q12 5 8 5 Q12 1 12 1 Q12 1 16 5 Q12 5 12 12" fill="currentColor"/>
+                <rect x="11.25" y="11" width="1.5" height="5" fill="currentColor"/>
+                <path d="M18 14 Q18 8 15 8 Q18 4 18 4 Q18 4 21 8 Q18 8 18 14" fill="currentColor" opacity="0.6"/>
+                <rect x="17.25" y="13" width="1.5" height="4" fill="currentColor" opacity="0.6"/>
+                <ellipse cx="12" cy="19" rx="9" ry="1.5" fill="currentColor" opacity="0.3"/>
+              </svg>
+            </div>
+            <h1>Change Password</h1>
+            {user?.must_change_password && (
+              <p className="login-subtitle login-warning">
+                You must change your password before continuing
+              </p>
+            )}
+          </div>
+
+          {error && (
+            <div className="login-error">
+              <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2">
+                <circle cx="12" cy="12" r="10"/>
+                <line x1="12" y1="8" x2="12" y2="12"/>
+                <line x1="12" y1="16" x2="12.01" y2="16"/>
+              </svg>
+              <span>{error}</span>
+            </div>
+          )}
+
+          <form onSubmit={handleSubmit} className="login-form">
+            <div className="login-form-group">
+              <label htmlFor="currentPassword">Current Password</label>
+              <input
+                id="currentPassword"
+                type="password"
+                value={currentPassword}
+                onChange={(e) => setCurrentPassword(e.target.value)}
+                placeholder="Enter current password"
+                autoComplete="current-password"
+                autoFocus
+                disabled={isSubmitting}
+              />
+            </div>
+
+            <div className="login-form-group">
+              <label htmlFor="newPassword">New Password</label>
+              <input
+                id="newPassword"
+                type="password"
+                value={newPassword}
+                onChange={(e) => setNewPassword(e.target.value)}
+                placeholder="Enter new password (min 8 characters)"
+                autoComplete="new-password"
+                disabled={isSubmitting}
+              />
+            </div>
+
+            <div className="login-form-group">
+              <label htmlFor="confirmPassword">Confirm New Password</label>
+              <input
+                id="confirmPassword"
+                type="password"
+                value={confirmPassword}
+                onChange={(e) => setConfirmPassword(e.target.value)}
+                placeholder="Confirm new password"
+                autoComplete="new-password"
+                disabled={isSubmitting}
+              />
+            </div>
+
+            <button
+              type="submit"
+              className="login-submit"
+              disabled={isSubmitting}
+            >
+              {isSubmitting ? (
+                <>
+                  <span className="login-spinner"></span>
+                  Changing password...
+                </>
+              ) : (
+                'Change Password'
+              )}
+            </button>
+          </form>
+        </div>
+
+        <div className="login-footer">
+          <p>Artifact storage and management system</p>
+        </div>
+      </div>
+    </div>
+  );
+}
+
+export default ChangePasswordPage;
diff --git a/frontend/src/pages/LoginPage.css b/frontend/src/pages/LoginPage.css
index a422802..bb9902e 100644
--- a/frontend/src/pages/LoginPage.css
+++ b/frontend/src/pages/LoginPage.css
@@ -69,6 +69,11 @@
   font-size: 0.875rem;
 }
 
+.login-subtitle.login-warning {
+  color: var(--warning);
+  font-weight: 500;
+}
+
 /* Error message */
 .login-error {
   display: flex;
diff --git a/frontend/src/pages/PackagePage.tsx b/frontend/src/pages/PackagePage.tsx
index dd5e422..80f4f33 100644
--- a/frontend/src/pages/PackagePage.tsx
+++ b/frontend/src/pages/PackagePage.tsx
@@ -1,7 +1,7 @@
 import { useState, useEffect, useCallback } from 'react';
-import { useParams, useSearchParams, useNavigate } from 'react-router-dom';
+import { useParams, useSearchParams, useNavigate, useLocation } from 'react-router-dom';
 import { TagDetail, Package, PaginatedResponse, AccessLevel } from '../types';
-import { listTags, getDownloadUrl, getPackage, getMyProjectAccess } from '../api';
+import { listTags, getDownloadUrl, getPackage, getMyProjectAccess, UnauthorizedError, ForbiddenError } from '../api';
 import { Breadcrumb } from '../components/Breadcrumb';
 import { Badge } from '../components/Badge';
 import { SearchInput } from '../components/SearchInput';
@@ -57,6 +57,7 @@ function CopyButton({ text }: { text: string }) {
 function PackagePage() {
   const { projectName, packageName } = useParams<{ projectName: string; packageName: string }>();
   const navigate = useNavigate();
+  const location = useLocation();
   const [searchParams, setSearchParams] = useSearchParams();
   const { user } = useAuth();
 
@@ -64,6 +65,7 @@ function PackagePage() {
   const [tagsData, setTagsData] = useState<PaginatedResponse<TagDetail> | null>(null);
   const [loading, setLoading] = useState(true);
   const [error, setError] = useState<string | null>(null);
+  const [accessDenied, setAccessDenied] = useState(false);
   const [uploadTag, setUploadTag] = useState('');
   const [uploadSuccess, setUploadSuccess] = useState<string | null>(null);
   const [artifactIdInput, setArtifactIdInput] = useState('');
@@ -98,6 +100,7 @@ function PackagePage() {
 
     try {
       setLoading(true);
+      setAccessDenied(false);
       const [pkgData, tagsResult, accessResult] = await Promise.all([
         getPackage(projectName, packageName),
         listTags(projectName, packageName, { page, search, sort, order }),
@@ -108,11 +111,21 @@ function PackagePage() {
       setAccessLevel(accessResult.access_level);
       setError(null);
     } catch (err) {
+      if (err instanceof UnauthorizedError) {
+        navigate('/login', { state: { from: location.pathname } });
+        return;
+      }
+      if (err instanceof ForbiddenError) {
+        setAccessDenied(true);
+        setError('You do not have access to this package');
+        setLoading(false);
+        return;
+      }
       setError(err instanceof Error ? err.message : 'Failed to load data');
     } finally {
       setLoading(false);
     }
-  }, [projectName, packageName, page, search, sort, order]);
+  }, [projectName, packageName, page, search, sort, order, navigate, location.pathname]);
 
   useEffect(() => {
     loadData();
@@ -234,6 +247,28 @@ function PackagePage() {
     return <div className="loading">Loading...</div>;
   }
 
+  if (accessDenied) {
+    return (
+      <div className="home">
+        <Breadcrumb
+          items={[
+            { label: 'Projects', href: '/' },
+            { label: projectName!, href: `/project/${projectName}` },
+          ]}
+        />
+        <div className="error-message" style={{ textAlign: 'center', padding: '48px 24px' }}>
+          <h2>Access Denied</h2>
+          <p>You do not have permission to view this package.</p>
+          {!user && (
+            <p style={{ marginTop: '16px' }}>
+              <a href="/login" className="btn btn-primary">Sign in</a>
+            </p>
+          )}
+        </div>
+      </div>
+    );
+  }
+
   return (
     <div className="home">
       <Breadcrumb
diff --git a/frontend/src/pages/ProjectPage.tsx b/frontend/src/pages/ProjectPage.tsx
index 876e776..6b8a99e 100644
--- a/frontend/src/pages/ProjectPage.tsx
+++ b/frontend/src/pages/ProjectPage.tsx
@@ -1,7 +1,7 @@
 import { useState, useEffect, useCallback } from 'react';
-import { useParams, Link, useSearchParams, useNavigate } from 'react-router-dom';
+import { useParams, Link, useSearchParams, useNavigate, useLocation } from 'react-router-dom';
 import { Project, Package, PaginatedResponse, AccessLevel } from '../types';
-import { getProject, listPackages, createPackage, getMyProjectAccess } from '../api';
+import { getProject, listPackages, createPackage, getMyProjectAccess, UnauthorizedError, ForbiddenError } from '../api';
 import { Breadcrumb } from '../components/Breadcrumb';
 import { Badge } from '../components/Badge';
 import { SearchInput } from '../components/SearchInput';
@@ -31,6 +31,7 @@ function formatBytes(bytes: number): string {
 function ProjectPage() {
   const { projectName } = useParams<{ projectName: string }>();
   const navigate = useNavigate();
+  const location = useLocation();
   const [searchParams, setSearchParams] = useSearchParams();
   const { user } = useAuth();
 
@@ -38,6 +39,7 @@ function ProjectPage() {
   const [packagesData, setPackagesData] = useState<PaginatedResponse<Package> | null>(null);
   const [loading, setLoading] = useState(true);
   const [error, setError] = useState<string | null>(null);
+  const [accessDenied, setAccessDenied] = useState(false);
   const [showForm, setShowForm] = useState(false);
   const [newPackage, setNewPackage] = useState({ name: '', description: '', format: 'generic', platform: 'any' });
   const [creating, setCreating] = useState(false);
@@ -75,6 +77,7 @@ function ProjectPage() {
 
     try {
       setLoading(true);
+      setAccessDenied(false);
       const [projectData, packagesResult, accessResult] = await Promise.all([
         getProject(projectName),
         listPackages(projectName, { page, search, sort, order, format: format || undefined }),
@@ -86,11 +89,21 @@ function ProjectPage() {
       setIsOwner(accessResult.is_owner);
       setError(null);
     } catch (err) {
+      if (err instanceof UnauthorizedError) {
+        navigate('/login', { state: { from: location.pathname } });
+        return;
+      }
+      if (err instanceof ForbiddenError) {
+        setAccessDenied(true);
+        setError('You do not have access to this project');
+        setLoading(false);
+        return;
+      }
       setError(err instanceof Error ? err.message : 'Failed to load data');
     } finally {
       setLoading(false);
     }
-  }, [projectName, page, search, sort, order, format]);
+  }, [projectName, page, search, sort, order, format, navigate, location.pathname]);
 
   useEffect(() => {
     loadData();
@@ -151,6 +164,23 @@ function ProjectPage() {
     return <div className="loading">Loading...</div>;
   }
 
+  if (accessDenied) {
+    return (
+      <div className="home">
+        <Breadcrumb items={[{ label: 'Projects', href: '/' }]} />
+        <div className="error-message" style={{ textAlign: 'center', padding: '48px 24px' }}>
+          <h2>Access Denied</h2>
+          <p>You do not have permission to view this project.</p>
+          {!user && (
+            <p style={{ marginTop: '16px' }}>
+              <a href="/login" className="btn btn-primary">Sign in</a>
+            </p>
+          )}
+        </div>
+      </div>
+    );
+  }
+
   if (!project) {
     return <div className="error-message">Project not found</div>;
   }
diff --git a/frontend/src/types.ts b/frontend/src/types.ts
index e020e1a..389601c 100644
--- a/frontend/src/types.ts
+++ b/frontend/src/types.ts
@@ -238,6 +238,7 @@ export interface User {
   username: string;
   display_name: string | null;
   is_admin: boolean;
+  must_change_password?: boolean;
 }
 
 export interface LoginCredentials {