Ankr Ethereum Bridge Deposit-Replay Exploit

On November 9, 2026, the Ankr Ethereum bridge was drained of about $303,600 when an attacker replayed a tiny, already-redeemed Optimism deposit to authorise five fraudulent withdrawals.

What happened

Ankr's bridge lets users move liquid-staking assets from one chain and withdraw them on another. The exploit abused the bridge's handling of already-redeemed deposits: all five fraudulent withdrawals referenced a single Optimism deposit from November 3 that had moved just 0.0044024803 ankrETH to Ethereum — an amount already withdrawn on Ethereum that same day. The attacker resubmitted that spent deposit, each time with modified receipt information, and the bridge failed to reject the reused receipt, authorising five outsized withdrawals to one wallet between roughly 08:09 and 08:12 UTC. The drained assets were 82.91 ankrETH ($216,370), 515,206 ankrPOL ($56,372) and about 7.98 million ANKR (~$30,857), plus unpriced aMATICb and aETHb. Security firm Blockaid flagged the ongoing exploit around 08:42 UTC, initially estimating about $292,000 across the five transactions; valuing the three priced tokens put the figure near $303,600. Reporting differed on root cause, with some outlets citing a compromised admin key and others the deposit-replay verification flaw.

Aftermath

Ankr did not immediately issue a public statement, and the bridge's on-chain pause flag still showed false well after the drain, leaving it unclear whether further withdrawals had been contained. No funds were recovered at the time of writing. The incident added to a long record of trouble for Ankr's infrastructure, which was previously hit in 2022 when an infinite-mint bug destroyed its aBNBc liquid-staking token on BNB Chain.

Why it matters

Ankr is a classic bridge replay-verification failure — the same bug class that lets attackers reuse messages or proofs to claim value they never bridged. Nomad Bridge fell in 2022 when a flawed initialisation made every message replayable, and bridges keep failing wherever a deposit receipt is not strictly tied to a single, un-redeemable withdrawal. That a dust-sized 0.0044 ankrETH deposit could be stretched into a six-figure drain underscores how little an attacker needs when a bridge fails to mark a deposit as spent. Even sub-$1M losses dent confidence in liquid-staking bridges, where user funds depend entirely on the accounting that binds a deposit on one chain to exactly one withdrawal on another.