Etherspot ResourceLockValidator — replayable signature proof

Source & credit. Reproduction of a public audit finding curated by AuditVault — the original finding: 61409-c-07-in-resourcelockvalidator-the-validateuserop-function-is. Standalone Foundry PoC and full write-up: 61409-c-07-resource-lock-validator-signature-proof-replay_exp in the evm-hack-registry mirror.

Vulnerability classes: vuln/bridge/replay · vuln/auth/signature-replay

Reproduction: local synthetic Foundry reduction; the complete passing trace is in output.txt.

Key info#

TL;DR#

The validator checks a ResourceLock Merkle proof but never consumes it. EntryPoint can therefore submit the same call data with a different nonce, and the wallet executes the signed action repeatedly.

Background#

ResourceLock authorization is intentionally narrower than ordinary account nonce validation. It must bind a proof to a one-time call (or maintain a nonce/consumed set) before returning validation success.

The vulnerable code#

The synthetic preserves the audited operation with an @> VULN marker:

function validate(bytes32 proof, uint256 /*nonce*/) external returns (bool) {
    validations++;
    // @> VULN: proof is accepted without recording it as consumed.
    return proof != bytes32(0);
}

Full source: test/61409-c-07-resource-lock-validator-signature-proof-replay.sol.

Root cause#

The validator treats the EntryPoint nonce as sufficient even though the signed hash is reconstructed from ResourceLock call data only. No proof hash is stored as consumed, so a fresh nonce does not create a fresh authorization.

Preconditions#

• A wallet has installed the ResourceLock validator and a valid signed proof exists.
• The EntryPoint accepts a subsequent nonce for the same call data.
• The validator is reached without a one-time proof/nonce check.

Attack walkthrough#

1. Exploit.run() validates PROOF with nonce 0 and executes the wallet.
2. It submits the identical PROOF with nonce 1; validate returns true again.
3. The wallet execution counter reaches 2, proving replay. The passing assertion is recorded at output.txt:355.

Diagrams#

Remediation#

Hash the nonce into the signed ResourceLock authorization and reject a proof hash already present in a consumed mapping. Mark it consumed atomically before executing the call.

How to reproduce#

cd evm-hack-registry/61409-c-07-resource-lock-validator-signature-proof-replay_exp
forge test -vvvvv

Sources#

• AuditVault finding #61409
• Shieldify Etherspot review
• Synthetic test

Reference: https://github.com/shieldify-security/audits-portfolio-md/blob/main/Etherspot-CredibleAccountModule-Security-Review.md

Sources & further analysis#

Reproductions & code

• Standalone PoC + full trace: 61409-c-07-resource-lock-validator-signature-proof-replay_exp (evm-hack-registry mirror).
• AuditVault finding: 61409-c-07-in-resourcelockvalidator-the-validateuserop-function-is.

Alerts & third-party analyses

• Web3Sec X hacked database: search.
• Rekt leaderboard: search.
• Solodit incident search: search.

These dashboards index community alerts tweets, post-mortems, and independent write-ups. Reach them through the protocol name above to cross-check this reproduction against other analyses.