> For the complete documentation index, see [llms.txt](https://reports.immunefi.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://reports.immunefi.com/quantus-or-audit-competition/89219-bc-low-missing-merkle-leaf-record-lead-to-permanent-freezing-of-the-miner-volume-fee.md). # 89219 bc low missing merkle leaf record lead to permanent freezing of the miner volume fee **Submitted on Aug 17th 2026 at 21:45:29 UTC by @Destiny0629 for** [**Audit Comp | Quantus**](https://immunefi.com/audit-competition/audit-comp-quantus) * **Report ID:** #89219 * **Report Type:** Blockchain/DLT * **Report severity:** Low * **Target:** * **Impacts:** * Contract fails to deliver promised returns, but doesn't lose value ## Description ## Brief/Intro Every wormhole exit pays the block author's miner-fee share to a keyless wormhole address through event-free `increase_balance` without recording a zk-tree leaf, permanently freezing that fee. ## Vulnerability Details **Affected component.** `pallet-wormhole` fee distribution inside the exit handler (`pallets/wormhole/src/lib.rs:954-985`) **Root cause.** Funds at a keyless wormhole address are spendable only through a ZK membership proof which requires a recorded leaf. The user-exit path mints and records a leaf (`increase_balance` at `lib.rs:838` + `record_transfer` at `:864`), and mining rewards do too (`:496`), but the miner-fee path mints through `increase_balance` at `lib.rs:965` with no `record_transfer` — so no leaf exists and the keyless recipient has no private key, leaving the credit permanently unspendable. **Trigger.** Ordinary block production: every exit that pays a nonzero volume fee in a block authored by a miner freezes that miner's fee share. This is distinct from the earlier Report-D F-03 issue (the address is now correctly derived, yet the credit is still frozen for lack of a leaf — an incomplete fix). ## Impact Details Permanent, systemic non-delivery of the miner's volume-fee share — credited to a keyless address with no zk-leaf, so it can never be withdrawn and is frozen forever. ## References * `pallets/wormhole/src/lib.rs:954-985` / `:965` — miner-fee `increase_balance` with no `record_transfer` * `pallets/wormhole/src/lib.rs:838` / `:864` — user-exit path: `increase_balance` + `record_transfer` (the correct pattern) * `pallets/wormhole/src/lib.rs:496` — mining-reward path: mint + `record_transfer` ## Recommended Mitigation Steps After minting the miner fee at `lib.rs:965`, record a zk-tree leaf for the author's wormhole address (mirroring the user-exit `record_transfer` at `:864`) so the miner can prove membership and withdraw it. ## Proof of Concept Add inside `mod private_batch_proof_tests` in `pallets/wormhole/src/tests.rs` (crate `pallet-wormhole`). Then run: ```bash cargo test -p pallet-wormhole exploit_miner_fee_frozen_no_leaf_recorded -- --nocapture ``` ```rust #[test] fn exploit_miner_fee_frozen_no_leaf_recorded() { new_test_ext().execute_with(|| { let proof = deserialize_test_proof(); let inputs = parse_private_batch_public_inputs(&proof).expect("parse"); let real_exits = inputs.account_data.iter().filter(|a| a.summed_output_amount > 0).count(); setup_valid_block_state_for_test_proof(); set_miner_preimage_digest([0xD0u8; 32]); // a miner authors this block let leaves_before = pallet_zk_tree::LeafCount::::get(); // The real permissionless unsigned extrinsic (ZK-verified in pre_dispatch). assert_ok!(Wormhole::verify_private_batch(RawOrigin::None.into(), get_test_proof_bytes())); let leaves_added = (pallet_zk_tree::LeafCount::::get() - leaves_before) as usize; let miner_fee_paid = System::events().iter().any(|r| matches!( r.event, RuntimeEvent::Wormhole(crate::Event::::MinerVolumeFeePaid { .. }) )); println!( "[F1] miner_fee_paid={}; leaves_added={} (== {} user exit(s); the miner fee added no leaf)", miner_fee_paid, leaves_added, real_exits ); assert!(miner_fee_paid, "the miner was paid a nonzero volume fee"); // The miner fee added no leaf: leaves grew only by the user-exit count, so the // keyless miner address can never build a membership proof to spend the fee. assert_eq!( leaves_added, real_exits, "only user exits record leaves; the miner-fee credit is leaf-less => frozen" ); }); } ``` ``` running 1 test [F1] miner_fee_paid=true; leaves_added=1 (== 1 user exit(s); the miner fee added no leaf) test tests::private_batch_proof_tests::exploit_miner_fee_frozen_no_leaf_recorded ... ok test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 87 filtered out; finished in 0.01s ``` --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://reports.immunefi.com/quantus-or-audit-competition/89219-bc-low-missing-merkle-leaf-record-lead-to-permanent-freezing-of-the-miner-volume-fee.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.