FLOW-3: Cross-VM state desync when completeProcessing fails after successful operation

[liobrasil]

Severity: Medium

Files Affected

• cadence/contracts/FlowYieldVaultsEVM.cdc
• solidity/src/FlowYieldVaultsRequests.sol

Description

YieldVault ownership is tracked on both EVM (validYieldVaultIds, yieldVaultOwners) and Cadence (yieldVaultsByEVMAddress, yieldVaultOwnershipLookup). If Cadence successfully creates/closes a vault but completeProcessing() fails, the two sides diverge.

This blocks users from subsequent EVM interactions because the EVM registry is not updated despite Cadence state changes. Users cannot create new requests if they've hit the pending limit, and manual intervention is required.

Common Root Cause (shared with FLOW-2 / FLOW-3 / FLOW-6)

startProcessing() transitions PENDING → PROCESSING but does not remove the request from pendingRequestIds / pendingRequestIdsByUser (removal only happens in completeProcessing()). If completeProcessing() reverts (e.g., ERC20 refund approval/transferFrom, or out-of-gas in _removePendingRequest()), the Worker does not revert the Cadence transaction, so Cadence-side state may commit while the EVM request remains PROCESSING in the pending queues. Since cancelRequest()/dropRequests() only operate on PENDING, there is no in-protocol escape hatch.

Example (Cadence commits, EVM finalize fails)

1. CREATE_YIELDVAULT succeeds on Cadence and ownership is recorded in yieldVaultsByEVMAddress / yieldVaultOwnershipLookup.
2. The Worker then calls EVM completeProcessing(success=true, ...), but the call reverts (e.g., out-of-gas in _removePendingRequest()), so EVM does not update validYieldVaultIds / yieldVaultOwners.
3. Result: Cadence and EVM ownership registries diverge, and the request can remain stuck in PROCESSING.

Recommendation

Implement a reconciliation mechanism or admin repair tools to detect and resolve registry divergence. Add monitoring for Cadence success events without corresponding EVM COMPLETED events.

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Parent Issue: #15

[vishalchangrani]

This will be addressed as part of the worker revamp that @nvdtf is working on.