Submitted by EV_om, also found by ArsenLupin
The ArbitrumDepositProcessorL1 contract is responsible for bridging OLAS tokens and messages from L1 to the ArbitrumTargetDispenserL2 contract on Arbitrum. When calling claimStakingIncentives() or claimStakingIncentivesBatch() on the Dispenser contract for a nominee on Arbitrum, it creates a retriable ticket via the Inbox.createRetryableTicket() function to send a message to Arbitrum to process the claimed incentives.
However, when creating this retriable ticket, the refundAccount is passed as both the excessFeeRefundAddress and callValueRefundAddress parameters. As per the Arbitrum documentation and code, specifying the callValueRefundAddress gives that address a critical permission to cancel the retriable ticket on L2.
This means an attacker can perform the following steps:
While the protocol could call processDataMaintenance() on L2 with the data from the cancelled message to recover, this would require passing a governance proposal. Given that this attack can be carried out any number of times (e.g. as often as possible and with a different target each time), this can considerably impact the functioning of the protocol hence I believe Medium severity is justified.
Attacker can grief the protocol by making legitimately claimed staking incentives irredeemable on L2. This would require governance intervention each time to recover the lost incentives.
Since no call value is ever sent with the ticket, the callValueRefundAddress can be left empty when creating the retryable ticket or an admin address passed instead, if the protocol wants to reserve the right to cancel tickets.
Access Control
kupermind (Olas) confirmed and commented:
Olas mitigated
Varun_05 (warden) commented:
