diff --git a/prdoc/pr_2811.prdoc b/prdoc/pr_2811.prdoc
new file mode 100644
index 000000000000..647fb4c8ccd4
--- /dev/null
+++ b/prdoc/pr_2811.prdoc
@@ -0,0 +1,13 @@
+title: "Interlacing removes the region on which it is performed."
+
+doc:
+  - audience: Runtime User
+    description: |
+      The current implementation of the broker pallet does not remove
+      the region on which the interlacing is performed. This can create
+      a vulnerability, as the original region owner is still allowed to 
+      assign a task to the region even after transferring an interlaced
+      part of it.
+
+crates:
+  - name: "pallet-broker"
diff --git a/substrate/frame/broker/src/dispatchable_impls.rs b/substrate/frame/broker/src/dispatchable_impls.rs
index b04e15b169bc..f2451013251f 100644
--- a/substrate/frame/broker/src/dispatchable_impls.rs
+++ b/substrate/frame/broker/src/dispatchable_impls.rs
@@ -234,6 +234,9 @@ impl<T: Config> Pallet<T> {
 		ensure!(!pivot.is_void(), Error::<T>::VoidPivot);
 		ensure!(pivot != region_id.mask, Error::<T>::CompletePivot);
 
+		// The old region should be removed.
+		Regions::<T>::remove(&region_id);
+
 		let one = RegionId { mask: pivot, ..region_id };
 		Regions::<T>::insert(&one, &region);
 		let other = RegionId { mask: region_id.mask ^ pivot, ..region_id };
diff --git a/substrate/frame/broker/src/tests.rs b/substrate/frame/broker/src/tests.rs
index e1b489bbe6e6..6aa9ca84fc41 100644
--- a/substrate/frame/broker/src/tests.rs
+++ b/substrate/frame/broker/src/tests.rs
@@ -602,6 +602,43 @@ fn interlace_works() {
 	});
 }
 
+#[test]
+fn cant_assign_unowned_region() {
+	TestExt::new().endow(1, 1000).execute_with(|| {
+		assert_ok!(Broker::do_start_sales(100, 1));
+		advance_to(2);
+		let region = Broker::do_purchase(1, u64::max_value()).unwrap();
+		let (region1, region2) =
+			Broker::do_interlace(region, Some(1), CoreMask::from_chunk(0, 30)).unwrap();
+
+		// Transfer the interlaced region to account 2.
+		assert_ok!(Broker::do_transfer(region2, Some(1), 2));
+
+		// The initial owner should not be able to assign the non-interlaced region, since they have
+		// just transferred an interlaced part of it to account 2.
+		assert_noop!(Broker::do_assign(region, Some(1), 1001, Final), Error::<Test>::UnknownRegion);
+
+		// Account 1 can assign only the interlaced region that they did not transfer.
+		assert_ok!(Broker::do_assign(region1, Some(1), 1001, Final));
+		// Account 2 can assign the region they received.
+		assert_ok!(Broker::do_assign(region2, Some(2), 1002, Final));
+
+		advance_to(10);
+		assert_eq!(
+			CoretimeTrace::get(),
+			vec![(
+				6,
+				AssignCore {
+					core: 0,
+					begin: 8,
+					assignment: vec![(Task(1001), 21600), (Task(1002), 36000)],
+					end_hint: None
+				}
+			),]
+		);
+	});
+}
+
 #[test]
 fn interlace_then_partition_works() {
 	TestExt::new().endow(1, 1000).execute_with(|| {