diff --git a/Cargo.lock b/Cargo.lock
index 8b47c991..68664480 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -8103,7 +8103,7 @@ dependencies = [
 
 [[package]]
 name = "pallet-shielded-pool"
-version = "0.16.0"
+version = "0.17.0"
 dependencies = [
  "ark-bn254",
  "ark-ff 0.5.0",
diff --git a/frame/shielded-pool/CHANGELOG.md b/frame/shielded-pool/CHANGELOG.md
index 6c00ae4c..a5ac0713 100644
--- a/frame/shielded-pool/CHANGELOG.md
+++ b/frame/shielded-pool/CHANGELOG.md
@@ -2,6 +2,20 @@
 
 All notable changes to `pallet-shielded-pool` will be documented in this file.
 
+## [0.17.0] - 2026-08-07
+
+### Security
+
+- **`private_transfer` rejects two equal non-dummy nullifiers.** Both slots
+  holding the same real nullifier would spend one input twice within a single
+  transfer: each clears the used-set check (neither is marked yet), and the
+  second `mark_as_used` is idempotent, so nothing downstream caught it. Pool
+  admission does not catch it either — `validate_unsigned` collapses equal
+  nullifiers into one `provides` tag rather than flagging the duplicate. The
+  proof is expected to bind the two inputs distinct, but the chain no longer
+  relies on that: `execute` now compares the non-dummy nullifiers directly (at
+  most two inputs) and refuses a duplicate with `NullifierAlreadyUsed`.
+
 ## [0.16.0] - 2026-08-07
 
 ### Security
diff --git a/frame/shielded-pool/Cargo.toml b/frame/shielded-pool/Cargo.toml
index 9b0521c1..ae846927 100644
--- a/frame/shielded-pool/Cargo.toml
+++ b/frame/shielded-pool/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "pallet-shielded-pool"
-version = "0.16.0"
+version = "0.17.0"
 description = "Shielded pool pallet for private transactions using ZK proofs"
 authors = ["Orbinum Team"]
 license = "GPL-3.0-or-later"
diff --git a/frame/shielded-pool/src/operations/private_transfer.rs b/frame/shielded-pool/src/operations/private_transfer.rs
index 28b3d8f1..7832b206 100644
--- a/frame/shielded-pool/src/operations/private_transfer.rs
+++ b/frame/shielded-pool/src/operations/private_transfer.rs
@@ -60,6 +60,15 @@ impl PrivateTransferOperation {
 			);
 		}
 
+		let non_dummy: sp_std::vec::Vec<&Nullifier> =
+			nullifiers.iter().filter(|n| n.0 != [0u8; 32]).collect();
+		if non_dummy.len() == 2 {
+			ensure!(
+				non_dummy[0] != non_dummy[1],
+				Error::<T>::NullifierAlreadyUsed
+			);
+		}
+
 		for commitment in commitments.iter() {
 			ensure!(commitment.is_canonical(), Error::<T>::InvalidPublicSignals);
 			ensure!(commitment.is_valid(), Error::<T>::InvalidPublicSignals);
@@ -301,6 +310,30 @@ mod tests {
 		});
 	}
 
+	#[test]
+	fn execute_two_equal_nullifiers_fails() {
+		new_test_ext().execute_with(|| {
+			MerkleRepository::add_historic_poseidon_root::<Test>(KNOWN_ROOT);
+
+			// The same non-dummy nullifier in both slots would spend one input
+			// twice: neither is in the used set yet, so both clear that check.
+			assert_noop!(
+				PrivateTransferOperation::execute::<Test>(
+					proof(),
+					KNOWN_ROOT,
+					nullifiers_of(&[0x20, 0x20]),
+					commitments_of(&[0x30, 0x31]),
+					memos_of(2),
+					0u32,
+					0u128,
+					None,
+					1,
+				),
+				crate::pallet::Error::<Test>::NullifierAlreadyUsed
+			);
+		});
+	}
+
 	#[test]
 	fn execute_memo_commitment_mismatch_fails() {
 		new_test_ext().execute_with(|| {