diff --git a/pkg/db/fixtures/api_tokens.yml b/pkg/db/fixtures/api_tokens.yml
index cad2dbe9b..b7a225616 100644
--- a/pkg/db/fixtures/api_tokens.yml
+++ b/pkg/db/fixtures/api_tokens.yml
@@ -38,3 +38,13 @@
   owner_id: 17
   created: 2023-09-01 07:00:00
   # token in plaintext is tk_disabled_user_test_token_000000001234abcd
+- id: 5
+  title: 'locked user token'
+  token_salt: xK9mPr2sNq
+  token_hash: ee3fb2381e42ec87430519de0b59ce5fbe6ad7e0f0be40948ac28100167ed6f26fc6999f53958f589536d6291418c9419aef
+  token_last_eight: 12345678
+  permissions: '{"tasks":["read_all"]}'
+  expires_at: 2099-01-01 00:00:00
+  owner_id: 18
+  created: 2023-09-01 07:00:00
+  # token in plaintext is tk_locked_user_test_token_0000000012345678
diff --git a/pkg/db/fixtures/users.yml b/pkg/db/fixtures/users.yml
index 9bbee147e..e3f23c58d 100644
--- a/pkg/db/fixtures/users.yml
+++ b/pkg/db/fixtures/users.yml
@@ -136,3 +136,12 @@
   issuer: local
   updated: 2018-12-02 15:13:12
   created: 2018-12-01 15:13:12
+# Locked user for security tests
+- id: 18
+  username: 'user18'
+  password: '$2a$04$X4aRMEt0ytgPwMIgv36cI..7X9.nhY/.tYwxpqSi0ykRHx2CwQ0S6' # 12345678
+  email: 'user18@example.com'
+  status: 3
+  issuer: local
+  updated: 2018-12-02 15:13:12
+  created: 2018-12-01 15:13:12
diff --git a/pkg/user/user_test.go b/pkg/user/user_test.go
index fb75dae7c..a5bc263c7 100644
--- a/pkg/user/user_test.go
+++ b/pkg/user/user_test.go
@@ -329,6 +329,16 @@ func TestCheckUserCredentials(t *testing.T) {
 		require.Error(t, err)
 		assert.True(t, IsErrAccountDisabled(err))
 	})
+	t.Run("locked user", func(t *testing.T) {
+		db.LoadAndAssertFixtures(t)
+		s := db.NewSession()
+		defer s.Close()
+
+		// user18 is locked (status=3), password is "12345678"
+		_, err := CheckUserCredentials(s, &Login{Username: "user18", Password: "12345678"})
+		require.Error(t, err)
+		assert.True(t, IsErrAccountLocked(err))
+	})
 }
 
 func TestUpdateUser(t *testing.T) {
diff --git a/pkg/webtests/api_tokens_test.go b/pkg/webtests/api_tokens_test.go
index e47f53a16..8434cd488 100644
--- a/pkg/webtests/api_tokens_test.go
+++ b/pkg/webtests/api_tokens_test.go
@@ -112,6 +112,21 @@ func TestAPIToken(t *testing.T) {
 		assert.Equal(t, http.StatusUnauthorized, res.Code)
 		assert.Contains(t, res.Body.String(), `"code":11`)
 	})
+	t.Run("locked user token rejected", func(t *testing.T) {
+		e, err := setupTestEnv()
+		require.NoError(t, err)
+		req := httptest.NewRequest(http.MethodGet, "/api/v1/tasks", nil)
+		res := httptest.NewRecorder()
+		c := e.NewContext(req, res)
+		h := routes.SetupTokenMiddleware()(func(c *echo.Context) error {
+			return c.String(http.StatusOK, "test")
+		})
+
+		req.Header.Set(echo.HeaderAuthorization, "Bearer tk_locked_user_test_token_0000000012345678") // Token 5 (locked user 18)
+		require.NoError(t, h(c))
+		assert.Equal(t, http.StatusUnauthorized, res.Code)
+		assert.Contains(t, res.Body.String(), `"code":11`)
+	})
 	t.Run("jwt", func(t *testing.T) {
 		e, err := setupTestEnv()
 		require.NoError(t, err)
diff --git a/pkg/webtests/caldav_test.go b/pkg/webtests/caldav_test.go
index 2ef0b3f7b..f0aa461d6 100644
--- a/pkg/webtests/caldav_test.go
+++ b/pkg/webtests/caldav_test.go
@@ -770,4 +770,13 @@ func TestCaldavDisabledUserRejected(t *testing.T) {
 		require.NoError(t, err)
 		assert.False(t, result, "disabled user should not be able to authenticate via CalDAV")
 	})
+	t.Run("locked user cannot authenticate via CalDAV", func(t *testing.T) {
+		e, _ := setupTestEnv()
+		c, _ := createRequest(e, http.MethodGet, "", nil, nil)
+
+		// user18 is locked (status=3), password is "12345678"
+		result, err := caldav.BasicAuth(c, "user18", "12345678")
+		require.NoError(t, err)
+		assert.False(t, result, "locked user should not be able to authenticate via CalDAV")
+	})
 }