Ledger has patched a vulnerability in certain Ethereum transaction-signing flows that could have allowed a malicious decentralized application (dApp) to substitute a transaction while the user was still reviewing it. The flaw sat at the security boundary between a dApp and Ledger's Ethereum signing process — the point at which users depend on the hardware wallet to confirm exactly which transaction they intend to authorize.

The vulnerability was publicly reported on Aug. 24, after security researchers identified a race-condition flaw in the Ethereum app's signing flow. According to the reports, an attacker could potentially exploit the signing process so that the device displayed one transaction while actually signing another.

How the attack could work

The risk centered on the interval between transaction review and final approval. A malicious dApp with access to the device connection could attempt to introduce different transaction data during that window.

Such a scenario would undermine one of the core protections of a hardware wallet: allowing users to verify transaction details on a trusted device before signing. Ledger's Ethereum tooling emphasizes human-readable transaction information through its Clear Signing architecture, which is designed to make approvals easier to verify.

Security reports say the vulnerability was reported to Ledger on Aug. 21, and researchers validated the behavior on a Ledger device. The issue was subsequently addressed in an update to the Ethereum app.

Users should update before signing

Ledger users who interact with Ethereum dApps should update Ledger Wallet and install the latest Ethereum app available for their device. Users should also continue checking transaction details directly on the hardware wallet before approving, since the relevant trust boundary is the moment the device shows what is being signed.

The vulnerability does not mean Ledger devices were generally compromised or that private keys were exposed. Rather, the reported issue concerned the integrity of the transaction data presented during one particular signing flow.

The incident also highlights why transaction verification remains important even when using hardware wallets, especially as Ethereum applications increasingly rely on smart-contract interactions that can be harder to read at a glance. Ethereum's broader Clear Signing initiative aims to strengthen that verification layer by showing users understandable transaction details rather than opaque contract data.