SushiSwap hacked, Head Chef says 'revoke all chains'

Quick Take

  • SushiSwap has fallen victim to an exploit.
  • Only users who have interacted with the decentralized exchange in the last four days seem to be affected.

Decentralized exchange SushiSwap has fallen victim to an exploit, which led to the loss of more than $3.3 million from at least one user, known as 0xSifu on Twitter.

The exploit involves an approve-related bug on the RouterProcessor2 contract — which PeckShield and SushiSwap Head Chef Jared Grey recommend revoking on all chains.

The root cause, according to Ancilia, Inc. and in technical terms, "is because in the internal swap() function, it will call swapUniV3() to set variable "lastCalledPool" which is at storage slot 0x00."

The cybersecurity account adds that "later on in the swap3callback function, the permission check gets bypassed."

To yoink, or notyoink?

In other words, by approving the bad contract, users unknowingly allow the exploiter to steal their tokens — or "yoink," in this case.

"The "yoink" function was used by the first attacker, which is due to the attack vector being a bug in the "approve" mechanism of the SushiSwap router contract," The Block Research Analyst Brad Kay says.

"The bug allows an unauthorized entity to essentially "yoink" tokens without the proper approval from the token owner," Kay explains, adding: "Following the first attack for 100 ETH — possibly a white hat — it seems like another hacker came along and stole another 1800-ish ETH using the same contract but instead named their function "notyoink."

THE SCOOP

Keep up with the latest news, trends, charts and views on crypto and DeFi with a new biweekly newsletter from The Block's Frank Chaparro

By signing-up you agree to our Terms of Service and Privacy Policy