TAC blockchain remains frozen for over 10 days after a massive exploit forces a 1.26 billion token bailout

The TAC network halt continues at block 24,671,475, more than 10 days after an exploit emptied the bonded staking pool. The network is an EVM-compatible Layer 1 connected to the TON ecosystem. An RPC query by CryptoSlate at 2:33 a.m. UTC still showed the final block from Aug. 22, meaning normal block production had not resumed.

The network's Sept. 1 postmortem put the drain at 2,985,651,403.40 TAC, or 28.6% of supply. TAC said one transaction reduced the bonded pool to zero without changing total token supply, leaving the chain's delegation records without the tokens that backed them.

The upstream Cosmos EVM advisory attributed the attack path to a mismatch between two balance records. The EVM StateDB tracked only an account's spendable tokens, while the Cosmos SDK ledger also tracked locked vesting tokens that could be delegated. Delegating more than the spendable amount caused an unchecked subtraction to wrap toward an enormous number close to 2^256.

Cosmos Labs said a second overflow operation then let an attacker zero a victim account while retaining its legitimate tokens. TAC identified the protocol-controlled staking pool as the victim account on its network. The advisory classed the flaw as critical and said Cosmos EVM versions below 0.6.2, plus versions 0.7.0 and 0.7.1, were vulnerable.