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Ankr Ethereum bridge exploited for nearly $300,000 in unauthorized withdrawals

Ankr's Ethereum cross-chain bridge has been exploited for approximately $292,000 after an attacker used a single small Optimism deposit to generate five forged withdrawal receipts that drained locked assets.

White Ankr logo and wordmark centered on a solid blue background.
Image: @Cointelegraph

Ankr's Ethereum cross-chain bridge was drained of roughly $292,000 across five unauthorized transactions, according to blockchain security firm Blockaid and independent tracking reports. Reports from Blockaid noted that the attack was ongoing as the intruder tapped the bridge contract to release locked inventory.[1][2][3][4][5][6]

Security analysts, including findings cited from Blockaid, PeckShield, and SlowMist, reported that the exploit originated from a single legitimate Optimism deposit of just 0.0044024803 ankrETH. The attacker reused this transaction to craft five forged withdrawal receipts. Although the tokens, amounts, and recipient addresses were altered, the receipts still carried valid consensus signatures that the vulnerable bridge contract accepted.[1][2][5][6]

The drained assets included 5,372 aMATICb, 515,200 ankrPOL worth around $56,000, 8 million ANKR valued at $30,700, and 83 ankrETH valued at roughly $192,000. Most of the stolen tokens were subsequently converted into 103 ETH, worth approximately $217,000.[2]

On-chain activity revealed additional anomalies ahead of the incident. Hours before the exploit occurred, multiple Ankr operator wallets on Ethereum, Arbitrum, and Linea were swept into a newly consolidated wallet, though whether operator infrastructure or signing keys were compromised remains unconfirmed.[2]

Key facts

  • Ankr's Ethereum cross-chain bridge was drained of approximately $292,000 across five transactions.
  • The attacker reused a single Optimism deposit of 0.0044024803 ankrETH to generate five forged withdrawal receipts.
  • The forged receipts retained valid consensus signatures despite modified recipient addresses, tokens, and withdrawal amounts.
  • Stolen tokens included 5,372 aMATICb, 515,200 ankrPOL (~$56,000), 8 million ANKR (~$30,700), and 83 ankrETH (~$192,000).
  • Most stolen assets were subsequently swapped into 103 ETH, valued at around $217,000.
  • Hours before the attack, several Ankr operator wallets across Ethereum, Arbitrum, and Linea were consolidated into a single wallet, though potential key compromise remains unconfirmed.

Sources 路 6 sources

  1. TB

    The Block@TheBlockCoPost on X 路

    NEW: Ankr's Ethereum cross-chain bridge has been exploited for nearly $300,000, according to security firm Blockaid. The attacker reportedly used a small Optimism deposit to withdraw the bridge's locked funds across five transactions, with Blockaid saying the exploit is still ongoing.

    Open source
  2. CP

    Crypto Patel@CryptoPatelPost on X 路

    ANOTHER DAY ANOTHER HACK: ethereum:0x8290333cef9e6d528dd5618fb97a76f268f3edd4 BRIDGE EXPLOITED: ~$300K DRAINED! Ankr's Ethereum cross-chain bridge was exploited through five unauthorized withdrawals, according to Blockaid, PeckShield and SlowMist. The attacker reportedly reused ONE legitimate Optimism transaction involving just 0.0044024803 ankrETH to create five forged withdrawal receipts. The receipts carried valid consensus signatures despite altered recipient addresses, tokens and withdrawal amounts. The bridge accepted them and released its locked assets. STOLEN ASSETS: 馃敼 5,372 aMATICb 馃敼 515.2K ankrPOL (~$56K) 馃敼 8M ANKR ($30.7K) 馃敼 83 ankrETH (~$192K) Most funds were reportedly swapped into 103 ETH (~$217K). ON-CHAIN EVIDENCE: Attacker: 0x9A88Dd45AE846A979705c9cFdfD0f229e592D703 Recipient: 0x119D250b82C1cf5345dF5912EFb4B1a4107a1Aa6 Vulnerable contract: 0xc437DF90B37C1dB6657339E31BfE54627f0e7181 Exploit transactions: 0x7310af5d5... 0x90c563360... 0xde2d5b455... 0x91ba1a9c8... 0x46e20d4c8... Reused Optimism transaction: 0x02e805b51... ANOTHER RED FLAG: Hours before the exploit, multiple Ankr operator wallets across Ethereum, Arbitrum and Linea were reportedly swept into a newly consolidated wallet. Whether operator infrastructure or signing keys were compromised remains unconfirmed. How can ONE legitimate deposit authorize FIVE withdrawals? This is a serious cross-chain verification failure that deserves answers. Stay alert. DYOR. @ankr

    Open source
  3. SI

    Solid Intel 馃摗@solidintel_xPost on X 路

    INTEL: Ankr Ethereum bridge drained of about $292,000 in an ongoing attack

    Open source
  4. CO

    Cointelegraph@CointelegraphPost on X 路

    馃毃 ALERT: An ongoing exploit has drained ~$292K from Ankr鈥檚 Ethereum bridge, per Blockaid. https://t.co/LLPqn9RVJq

    Open source
  5. CB

    Crypto Banter@crypto_banterPost on X 路

    馃毃ANKR ETHEREUM BRIDGE HIT BY ONGOING EXPLOIT! @Blockaid detected an attacker submitting five withdraw calls on Ankr鈥檚 Ethereum cross-chain bridge, using a tiny Optimism deposit to unlock the bridge鈥檚 full locked inventory. Around $292k has been drained so far across roughly five transactions, with the attack still ongoing.

    Open source
  6. CN

    crypto.news@cryptodotnewsPost on X 路

    BREAKING: Blockaid detects an ongoing Ankr鈥檚 Ethereum bridge exploit Blockaid has said that an attacker used a tiny Optimism deposit to trigger five withdrawal calls on Ankr鈥檚 Ethereum cross-chain bridge, unlocking its entire locked inventory and draining approximately $292,000 across five transactions so far.

    Open source