EigenLayer — Beacon chain withdrawals at lastWithdrawalTimestamp are lost

Source & credit. Reproduction of a public audit finding curated by AuditVault — the original finding: 40684-beacon-chain-withdrawals-that-occur-at-lastwithdrawaltimesta. Standalone Foundry PoC and full write-up: 40684-beacon-chain-withdrawals-that-occur-at-lastwithdrawaltimesta_exp in the evm-hack-registry mirror.

Vulnerability classes: frozen-funds · locked-funds · timestamp-dependence

Reproduction: self-contained Foundry PoC with only forge-std — no fork. output.txt · test/40684-…sol.

AuditVault taxonomy: lang/solidity · platform/cantina · severity/high · sector/restaking · sector/staking · genome: frozen-funds · locked-funds · timestamp-dependence

Key info#


Impact	HIGH — 32 ETH beacon withdrawal permanently stuck when restaking is activated in the same block
Protocol	EigenLayer — `EigenPod.proofIsForValidTimestamp` / `activateRestaking`
Vulnerable code	`timestamp > mostRecentWithdrawalTimestamp` (should be `>=`)
Bug class	Off-by-one timestamp guard / EIP-4895 ordering
Finding	Cantina — EigenLayer, Mar 2024 · #40684 · reporter hash
Report	cantina_competition_eigenlayer_mar2024.pdf
Source	AuditVault
Fix	Use `>= mostRecentWithdrawalTimestamp`
Compiler	`^0.8.24` (PoC)

TL;DR#

activateRestaking sets mostRecentWithdrawalTimestamp = block.timestamp and sweeps pod ETH.
Beacon-chain withdrawals for that timestamp execute after user txs (EIP-4895).
verifyAndProcessWithdrawals requires timestamp > mostRecentWithdrawalTimestamp.
A proof for the same timestamp is rejected — the ETH can never be claimed.

Diagrams#

sequenceDiagram participant User participant Pod as EigenPod participant Beacon as Beacon chain EIP-4895 User->>Pod: activateRestaking at T Note over Pod: mostRecentWithdrawalTimestamp = T, balance swept Beacon->>Pod: credit 32 ETH withdrawal at T after user txs User->>Pod: verifyAndProcessWithdrawals proof ts=T Pod-->>User: revert timestamp not greater than mostRecent Note over Pod: 32 ETH stuck forever

Impact#

Beacon withdrawals that share a block/timestamp with activateRestaking (or any _processWithdrawalBeforeRestaking) are unrecoverable under the strict > guard.

Sources#

AuditVault #40684
Cantina EigenLayer Mar 2024
Reduced from EigenPod.sol (proofIsForValidTimestamp, _processWithdrawalBeforeRestaking) as quoted in the finding; fixed form appears in Layr-Labs/eigenlayer-contracts@v0.2.3-mainnet-m2 with >=

Sources & further analysis#

Reproductions & code

Standalone PoC + full trace: 40684-beacon-chain-withdrawals-that-occur-at-lastwithdrawaltimesta_exp (evm-hack-registry mirror).
AuditVault finding: 40684-beacon-chain-withdrawals-that-occur-at-lastwithdrawaltimesta.

Alerts & third-party analyses

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Solodit incident search: search.

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