Ledger Error 0x6700: WRONG_LENGTH APDU Buffer Framing Fix
Ledger error 0x6700 is the ISO 7816-4 status word for "WRONG_LENGTH". It occurs when the length byte (`Lc`) specified in an APDU command header does not match the exact number of bytes contained in the payload, or exceeds the maximum frame buffer supported by the device coin app. This frequently affects users signing large multicall transactions, complex NFT batch trades, or L2 rollup calldata payloads.
# Root Cause & Technical Architecture
In ISO 7816-4 framing, byte 4 specifies `Lc` (Length of command data). Legacy Ledger coin apps allocate fixed-size static RAM buffers (typically 255 bytes per APDU chunk). If a web3 library attempts to send an unchunked calldata buffer exceeding 255 bytes, or miscalculates the `Lc` byte during packet assembly, the BOLOS memory protection manager aborts execution and returns `0x6700` to prevent buffer overflow attacks.
# 4-Step Actionable Diagnostic Protocol
Step-by-Step ResolutionSplit Complex Batch Transactions into Smaller Calls
If executing multi-action DeFi interactions (e.g., approve + deposit + stake in a single multicall), break the interaction into separate transactions.
Update Device App for Extended APDU Framing
Modern versions of the Ledger Ethereum application support extended APDU framing and streaming calldata chunking. Update your app via Ledger Live.
Inspect Viem / Ethers Serializer Chunking
Ensure your frontend or script uses `@ledgerhq/hw-app-eth` version 6.x or newer, which handles automatic chunking of payloads exceeding 255 bytes.
Check Derivation Path Data Length
Ensure the BIP-32 derivation path array is properly serialized (typically 1 byte for path length, followed by 4 bytes per path component).
# Diagnostic Verification Code / Command
typescript// Secure APDU Streaming Chunking for Large Payloads
import Eth from "@ledgerhq/hw-app-eth";
async function signLargeTransaction(transport: any, rawTxHex: string) {
const eth = new Eth(transport);
// hw-app-eth automatically chunks payloads into 255-byte frames
// preventing 0x6700 (WRONG_LENGTH) buffer framing errors
const result = await eth.signTransaction("44'/60'/0'/0/0", rawTxHex);
return result;
}Launch ERC-4337 UserOp Decoder
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# Frequently Asked Questions
FAQ SchemaWhy does 0x6700 happen on Uniswap Universal Router?
Universal Router transactions combine multiple token swaps and Permit2 approvals into one huge calldata payload that exceeds default single APDU buffers.
Does error 0x6700 indicate a corrupt Ledger memory?
No. It simply means the computer sent a data packet whose stated length header did not match the actual byte count received.
Can I bypass 0x6700 by increasing gas limits?
No. Gas limits are an on-chain EVM parameter, whereas 0x6700 is a hardware communication buffer framing error between your computer and the Ledger.