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0x6beb21b53f5b205c088570333ec875b720e333b49657f7026b01ed72b026851e0x56ff4afd909aa66a1530fe69bf94c74e6d44500cEthereum0x85705829c2f71ee3c40a7c28f6903e7c797c9433EthereumAn unprivileged attacker drained the APEMAGA/WETH Uniswap V2 pool in Ethereum block 20175377 via transaction 0x6beb21b53f5b205c088570333ec875b720e333b49657f7026b01ed72b026851e. The attacker first destroyed nearly the entire APEMAGA balance held by the pair, then called sync(), and finally sold attacker-held APEMAGA into the now-mispriced pool to extract 9.375657576473649845 WETH.
The root cause is a token-side arbitrary-balance burn primitive. The verified APEMAGA token contract at 0x56ff4afd909aa66a1530fe69bf94c74e6d44500c exposes family(address) as a public entrypoint, and that function routes into an internal routine that burns approximately 99.9% of the chosen account's balance without authorization. Because the pair address can be supplied directly, any unprivileged user can rewrite the pair's observable token reserve and then exploit Uniswap V2 reserve synchronization.
The victim pool is the Uniswap V2 pair 0x85705829c2f71ee3c40a7c28f6903e7c797c9433, which holds APEMAGA and WETH. Uniswap V2 pairs trust live ERC-20 balances as the source of truth and update their stored reserves when sync() is called. If an external bug changes a token balance inside the pair without a corresponding swap or liquidity event, the AMM will still accept the manipulated balance as canonical once sync() executes.
The APEMAGA token is not a standard ERC-20 implementation despite its surface naming. Its verified source embeds a second _approve_ routine that is not allowance logic; instead, it burns from an arbitrary account chosen by the caller. That breaks the basic invariant that unrelated callers must not be able to reduce another account's token balance or total supply.
This is an ATTACK-class incident caused by a permissionless arbitrary-balance burn in the token contract. The critical externally reachable function is family(address account), which forwards directly into _approve_(account, account, 0). Inside _approve_, the contract computes accountBalance = (_balances[owner] + trading()) * 999 / 1000 and subtracts that amount from _balances[owner] and _totalSupply, emitting a burn-style Transfer to the zero address.
That behavior means any caller can target the Uniswap pair address and destroy nearly all of the pair's APEMAGA balance in-place. Once the attacker calls sync(), the pair records the manipulated low token reserve while its WETH reserve remains intact. The attacker can then sell a comparatively small amount of APEMAGA into the pool and receive almost all of the WETH. The exploit is deterministic and requires no privileged role, private key, flash loan, or attacker-specific artifact.
The verified victim source shows the exploit primitive directly:
function _approve_(
address owner,
address spender,
uint256 amount
) internal virtual {
require(owner != address(0), "ERC20: burn from the zero address");
require(owner == spender, "ERC20: burn to the owner address");
uint256 accountBalance = (_balances[owner] + trading()) * 999 / 1000;
_balances[owner] -= accountBalance;
_totalSupply -= accountBalance;
emit Transfer(owner, address(0), accountBalance);
}
function family(address account) external {
super._approve_(account, account, 0);
}
This code makes the invariant failure explicit: an arbitrary external caller can pick any account, including the live AMM pair. The exploit trace confirms that exact mechanism. In the collected transaction trace, the helper contract calls Tonken::family(0x85705829c2f71EE3c40A7C28f6903e7c797c9433) twice, producing burn events of 53328645376776709609 and 53328645376776710 APEMAGA units from the pair. The trace then shows 0x85705829c2f71EE3c40A7C28f6903e7c797c9433::sync() emitting:
emit Sync(: 53382027404181, : 9384075748093369217)
That leaves the pair with only 53382027404181 APEMAGA units against 9384075748093369217 WETH wei, creating a fabricated reserve ratio. The attacker then transfers 59632616815636881 APEMAGA into the pair and executes the final router swap. The same trace shows:
WETH9::transfer(0xCe3B42e93Dd6313e413CbdB604e295908d3C7C85, 9375657576473649845)
emit Sync(: 59685998843041062, : 8418171619719372)
The balance-diff artifact independently matches the outcome: the pair's APEMAGA balance falls from 53382027404180890500 to 59685998843041062, and 0xce3b42e93dd6313e413cbdb604e295908d3c7c85 receives the extracted WETH proceeds. The exploit therefore does not depend on a hidden off-chain condition; it is the direct consequence of a public burn primitive being composable with Uniswap reserve synchronization.
The adversary cluster for the observed incident consists of sender EOA 0xb297735e9fb3e695ccce3963bfe042f318901ea0, helper contract 0x8de6314058c0b7eea809881d73e69b425c01f0b5, and profit recipient 0xce3b42e93dd6313e413cbdb604e295908d3c7c85. The on-chain execution is a single public transaction and can be reproduced by any unprivileged replacement attacker with fresh addresses.
The flow is:
family(pair) repeatedly against the public APEMAGA token until the pair balance collapses by several orders of magnitude.sync() on the Uniswap pair so the manipulated token balance becomes the stored reserve.The critical trace segment is:
Tonken::family(0x85705829c2f71EE3c40A7C28f6903e7c797c9433)
Tonken::family(0x85705829c2f71EE3c40A7C28f6903e7c797c9433)
0x85705829c2f71EE3c40A7C28f6903e7c797c9433::sync()
0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D::swapExactTokensForTokens(...)
WETH9::transfer(0xCe3B42e93Dd6313e413CbdB604e295908d3C7C85, 9375657576473649845)
This sequence is sufficient to realize the ACT opportunity because every invoked contract surface is publicly callable and the helper contract is not essential to exploitability.
The measurable pool loss is 9375657576473649845 wei of WETH, or 9.375657576473649845 WETH. The exploit also destroyed market integrity for the APEMAGA/WETH pool because the pair reserve ratio was forced to a fabricated state before the terminal swap. The affected public components are the APEMAGA token contract at 0x56ff4afd909aa66a1530fe69bf94c74e6d44500c and the APEMAGA/WETH pair at 0x85705829c2f71ee3c40a7c28f6903e7c797c9433.
0x6beb21b53f5b205c088570333ec875b720e333b49657f7026b01ed72b026851e0x56ff4afd909aa66a1530fe69bf94c74e6d44500c0x85705829c2f71ee3c40a7c28f6903e7c797c94330x7a250d5630b4cf539739df2c5dacb4c659f2488dfamily(address) and _approve_()sync(), and final WETH transfer