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Reproduced Exploit

Autonomint — `ABONDToken::transferFrom` corrupts `userStates` and enables Treasury ETH theft

1. transferFrom debits the from State, then writes it to msg.sender. 2. The true from keeps their full ethBacked State; the spender inherits a quasi-copy of the rich State. 3. redeemYields pays aBondAmount * ethBacked / PRECISION using the

Nov 2024•Other•accounting•3 min read

Chain

Other

Category

accounting

Date

Nov 2024

Source

AuditVault

PoC & write-upPoC for your local evm-hack-analyzerAuditVault PoCs

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Source & credit. Reproduction of a public audit finding curated by AuditVault — the original finding: 45462-h-9-abondtokentransferfrom-does-not-work-as-intended-and-all. Standalone Foundry PoC and full write-up: 45462-h-9-abondtokentransferfrom-does-not-work-as-intended-and-all_exp in the evm-hack-registry mirror.

Vulnerability classes: vuln/accounting/state-key · vuln/token/erc20-inconsistency · vuln/logic/direct-drain

Reproduction: a self-contained Foundry PoC that compiles & runs in an isolated project with only forge-std — no fork, no RPC, no anvil_state. Full trace: output.txt. PoC: test/45462-h-9-abondtokentransferfrom-does-not-work-as-intended-and-all_exp.sol.

AuditVault taxonomy: lang/solidity · sector/lending · sector/stable · sector/token · platform/sherlock · has/github · has/poc · severity/high · impact/loss-of-funds/direct-drain · genome: missing-modifier · direct-drain · liquidation-underwater · reentrancy-guard · timestamp-dependence

Key info#

ImpactHIGH — duplicated high-ethBacked State on the spender lets them redeem inflated ETH from Treasury
ProtocolAutonomint Colored Dollar V1 — ABONDToken.transferFrom
Vulnerable codeuserStates[msg.sender] = fromState after _debit (should be userStates[from])
Bug classWrong mapping key / dual-ledger ERC20
FindingSherlock — 2024-11-autonomint · #45462 (H-9) · reporter tjonair
Report2024-11-autonomint-judging
SourceAuditVault
StatusAudit finding. Reproduced here as a standalone local PoC.
Compiler^0.8.24 (PoC)

TL;DR#

  1. transferFrom debits the from State, then writes it to msg.sender.
  2. The true from keeps their full ethBacked State; the spender inherits a quasi-copy of the rich State.
  3. redeemYields pays aBondAmount * ethBacked / PRECISION using the duplicated State against the spender's ERC20 balance.
  4. A poor account can redeem ~2× ETH after transferFrom-ing 1 wei from a rich account.

The vulnerable code#

SOLIDITY
fromState = Colors._debit(fromState, uint128(value));
userStates[msg.sender] = fromState; // @> VULN: should be userStates[from]
super.transferFrom(from, to, value);

Fix:

DIFF
-       userStates[msg.sender] = fromState;
+       userStates[from] = fromState;

Root cause#

Dual accounting (ERC20 balances + colored userStates) updates the wrong address key after debit, breaking EIP-20 semantics and yield redemption.

Preconditions#

  • Account with high ethBacked approves the attacker.
  • Attacker holds some ABOND with lower ethBacked.
  • Treasury has ETH to pay redemptions.

Attack walkthrough#

  1. account1: 100 ABOND, ethBacked=2e18. account2: 10 ABOND, ethBacked=1e18.
  2. account1 approves account2 for 1 wei; account2 transferFrom → account3.
  3. account2's userStates now carries ethBacked=2e18.
  4. account2 redeems 10 ABOND → ~20 ETH instead of ~10 ETH.

Diagrams#

sequenceDiagram participant A1 as account1 rich participant A2 as account2 attacker participant T as ABONDToken participant Tr as Treasury A1->>T: approve A2 for 1 A2->>T: transferFrom A1 to A3 amount 1 Note over T: userStates[A2] = debited rich State A2->>Tr: redeemYields A2 bal Tr-->>A2: ETH at inflated ethBacked

Impact#

Treasury ETH theft; broken ABOND accounting; EIP-20 non-compliance for colored state.

Sources#

Sources & further analysis#

Reproductions & code

Alerts & third-party analyses

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

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