pNetwork pBTC-on-BSC bridge hack — September 2021

On 19 September 2021 at 17:20 UTC an attacker took 277 BTC — most of the collateral backing pBTC on BNB Chain — from pNetwork's cross-chain bridge. pNetwork's post-mortem attributes the loss to the code that read peg-out requests from event logs: the Rust routine extracting those events did not check that they had actually been emitted by pNetwork's own contracts. The attacker deployed contracts that emitted forged peg-out events alongside a legitimate one, and the bridge processed all of them, releasing the underlying bitcoin to addresses the attacker controlled.

Only the pBTC-on-BNB-Chain bridge was drained. pNetwork said attempts against pBTC on Ethereum and against its TLOS, PNT and pSAFEMOON bridges failed, and that other collateral was unaffected. The team's statement read: "an attacker was able to leverage a bug in our codebase and attack pBTC on BSC, stealing 277 BTC (most of its collateral)".

Dollar figures published at the time vary with the bitcoin price used: Crypto Briefing reported $12.4 million, Yahoo Finance $12.7 million, and Halborn later described it as over $13 million. The underlying quantity, 277 BTC, is stated by pNetwork itself and is not in dispute.

pNetwork offered a $1.5 million bounty for the funds' return. It went unanswered, the bitcoin was never recovered, and the receiving addresses were blacklisted with exchanges. The pNetwork DAO then approved a compensation plan for affected holders in two stages: an NFT series each redeemable for 400 PNT, followed by monthly PNT distributions with a fast-track option valuing PNT at $0.80. Claims ran into at least September 2022.