Zilliqa said a severe flaw in its Ledger application affected Schnorr signature generation for native, non-EVM Zilliqa transactions.
The project said the bug was present in all versions of the Zilliqa Ledger app released between 2019 and 2026. It detected on-chain signs of possible active exploitation on July 19 and confirmed the root cause on July 21.
The bug made signing nonces predictable
According to Zilliqa, the issue made the temporary nonce used during signing predictable. That meant an attacker could reconstruct a signer’s private key using only public on-chain data.
The root cause was traced to the signing program copying the wrong byte range when writing the nonce into a buffer. As a result, the top 64 bits of every generated nonce were fixed at zero, severely reducing entropy.
Five or more affected signatures could be enough
Zilliqa said that with five or more affected signatures, an attacker could recover a private key within seconds through lattice reduction. Because the impacted transactions are permanently recorded on-chain, updating the signing application cannot undo the risk. The related private keys must be abandoned.
Native transactions paused as fixes are finalized
Zilliqa advised users who had used a Ledger device to sign native Zilliqa transactions to wait for official guidance and not take independent action for now.
Native transactions have been paused to prevent further losses, and a coordinated remediation plan is in its final stage of confirmation. Zilliqa added that EVM transactions and the zilliqa-js, gozilliqa-sdk, and pyzil SDKs are not affected.