An unidentified vault on Base, the Ethereum layer-2 (L2) network incubated by Coinbase, lost about 1,783 wrapped staked Ether (wstETH), worth roughly $6 million, on Sunday, October 4, 2026.
Blockchain security firms said a newly deployed contract gained whitelist access to the vault and borrowed against its position on Aave V3 before the assets were moved to an attacker-controlled address. The loss grew from about $2 million to $6 million while the attack was still in progress.
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How the Base Vault Exploit Unfolded
Web3 security firm Blockaid was the first to publicly flag the incident. At 09:20 UTC (Coordinated Universal Time), it reported an ongoing exploit on an unnamed vault on Base. According to Blockaid, a brand-new contract had been added to the vault’s whitelist, a list of addresses permitted to interact with the vault’s funds. That contract borrowed aBaswstETH and forwarded the tokens to the attacker’s contract.
At the time, Blockaid estimated that about $2.02 million had been drained across roughly four transactions. In a follow-up post in the same thread, the firm said total losses had passed $6 million and the attack was still ongoing. One transaction cited by Blockaid is publicly viewable on BaseScan, the block explorer for Base.
Blockchain security firm PeckShield said at 09:56 UTC that address 0x0B..dB034 had drained 1,783 wstETH, valued at about $6 million, on Base.
Three minutes later, at 09:59 UTC, CertiK’s alert account described a newly deployed proxy contract borrowing about 1,783 aBaswstETH from vault 0xD1..FCABC. CertiK said the tokens were redeemed through Aave into roughly 1,783 wstETH held at the attacker’s address.
Security firm ExVul gave the most detailed count at 10:09 UTC. It put the loss at 1,783.067 aBaswstETH across six outflows from the vault and identified the contract receiving the stolen funds as 0xcd..F569d.
What Was Taken and How It Works
wstETH is the wrapped, non-rebasing version of stETH, the staked Ether token issued by liquid staking protocol Lido. Unlike stETH, its balance does not change daily. Instead, its value in Ether grows as staking rewards accrue.
aBaswstETH is the interest-bearing receipt token, known as an aToken, that Aave V3 issues on Base when users supply wstETH to the lending protocol. Holders can redeem aTokens for the underlying asset.
Based on the security firms’ descriptions, the attacker’s path was a borrow against the vault’s collateral, followed by redemption of the aTokens into wstETH. There is no public evidence that Aave’s core lending contracts or the Base network were compromised.
Victim Vault Holds Large Aave Positions on Base
The victim contract is a TransparentUpgradeableProxy, a standard OpenZeppelin smart contract design that lets an administrator upgrade a contract’s logic without changing its address.
Portfolio trackers show the address has held large Aave V3 positions on Base, with tens of millions of dollars in supplied assets against substantial borrows. That profile fits a managed vault or yield strategy built on top of Aave, rather than a core Aave market. No team or protocol has publicly identified itself as the vault’s operator.
Whitelist Change Was Signed by the Vault’s Own Multisig
The most significant detail so far comes from ExVul’s follow-up timeline. According to ExVul, the vault owner’s Safe, a multisignature (multisig) smart contract wallet that requires several approvals for each transaction, removed the attacker contract from the whitelist at 08:52 UTC. One minute later, at 08:53 UTC, the same Safe re-enabled it.
ExVul said both administrative transactions showed three successful Elliptic Curve Digital Signature Algorithm (ECDSA) signature recoveries under the same signing identities. In simple terms, the changes carried valid approvals from the Safe’s existing signers. The first borrow came about 70 seconds after the contract was re-enabled.
This places the focus on how those approvals were obtained, rather than on a flaw in Aave or in the vault’s lending logic. Whether the signers’ keys were compromised, a signing process was manipulated, or another failure occurred has not been confirmed by any party.
Where the Stolen wstETH Went
Activity on the attacker’s address shows interactions with the loot contract, a withdrawal routed through the Aave Base pool proxy and later calls involving the Lido wstETH token on Base.
Unverified community tracking has pointed to part of the proceeds beginning a bridge to Ethereum through Lido infrastructure, a process that typically takes several days. As of the latest BaseScan snapshot, the attacker address no longer holds a material wstETH balance and shows only a small amount of ETH.
As of publication, no protocol has claimed the vault, issued a post-mortem, frozen funds or announced a recovery effort or bounty offer.
Fourth Aave-Linked or Base Incident in a Week
The incident adds to a run of exploits involving Aave-linked infrastructure and Base. On October 2, The Crypto Times reported that a FlashLoopAdapter exploit drained about $305,000 from two Safe wallets running leveraged Aave V3 loops, an attack in which Aave’s core pools were used but not broken. A day later, GoldPesa’s GPXHooks contract was allegedly drained for $114,000 on Base.
The broader backdrop is also severe. September 2026 was the year’s worst month for crypto losses at about $766.4 million, according to CertiK, while hackers had already drained $972 million across the top 10 incidents of the first half.
The October 4 Base vault hack currently stands as an access-control failure on an unidentified vault, not a systemic breach of Aave or Base. A full account will depend on the vault’s operator identifying itself and explaining how a contract it had just removed from its whitelist was approved again within a minute.
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