Persistence: empty funds list locks 100 of Alice's LST

Source & credit. Reproduction of a public audit finding curated by AuditVault — the original finding: 53505-prst-5-user-can-lock-and-stake-arbitrary-amount-of-tokens-wi. Standalone Foundry PoC and full write-up: 53505-prst-5-user-can-lock-and-stake-arbitrary-amount-of-tokens-wi_exp in the evm-hack-registry mirror.

Vulnerability classes: vuln/logic/missing-check

Key info#


Protocol	Persistence
Finding	Hexens PRST-5, AuditVault 53505
Vulnerable code	`Locker.lockLstAsset`
Harm	Bob locks 100 with an empty funds list and joinPool pays him Alice's 100 LST. The fixed locker reverts and her 100 stays.
Chain	local synthetic

TL;DR#

The amount check runs only when funds contains the denom. An empty list skips it, then the lock balance still increases. joinPool pays that credit from the tokens Alice deposited.

The vulnerable code#

SOLIDITY

        // @> VULN: lock credit increases even when funds contained no matching coin
        locked_amount = locked_amount + asset.amount;

Root cause#

Nothing requires that the funds loop actually matched the denom before the credit is stored.

Preconditions#

Alice has locked 100 ux and the contract holds those tokens. Bob can call lock with an empty coin list.

Attack walkthrough#

Alice locks 100 and pays 100 LST. See output.txt.
The credit line runs for her paying call.
Bob locks 100 with an empty funds array. No tokens move.
Bob's lock record is 100.
joinPool transfers 100 to Bob.
The locker balance is 0 and Alice's credit is still 100. The fixed path reverts the unpaid lock.

Diagrams#

flowchart TD A["Alice pays 100 into the locker"] --> B["Bob locks 100 with no coins"] B["Bob locks 100 with no coins"] --> C["Credit increases anyway"] C["Credit increases anyway"] --> D["joinPool pays Bob"] D["joinPool pays Bob"] --> E["Alice's 100 is gone"]

Impact#

Alice loses 100 LST. Bob paid nothing. The fixed locker reverts unless a matching coin was pulled.

Remediation#

Require that a coin of the locked denom was received for the full amount before increasing the lock balance.

How to reproduce#

BASH

cd 53505-prst-5-user-can-lock-and-stake-arbitrary-amount-of-tokens-wi_exp
forge test -vv

Sources & further analysis#

Reproductions & code

Standalone PoC + full trace: 53505-prst-5-user-can-lock-and-stake-arbitrary-amount-of-tokens-wi_exp (evm-hack-registry mirror).
AuditVault finding: 53505-prst-5-user-can-lock-and-stake-arbitrary-amount-of-tokens-wi.

Alerts & third-party analyses

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

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