Mempool Pinning
mempool · security
A tactic that makes an unconfirmed transaction difficult to replace or fee-bump, delaying confirmation.
1.definition
Mempool pinning occurs when a transaction is structured so policy limits make replacement or fee-bumping difficult. It is usually not a consensus attack: the transaction may be valid, but nodes and miners may refuse the replacement or package needed to move it quickly.
2.mitigation
Wallets reduce pinning risk by keeping dependency chains simple, avoiding unnecessary shared inputs, and using fee-bumping strategies that match current relay policy. Package relay improvements can help nodes evaluate related transactions together, but support varies by network and implementation.
Related terms
Mempool
→A node’s local collection of valid transactions waiting to be included in a block.
blockchain · node
CPFP
→A fee-bumping technique where a high-fee child spends an unconfirmed output so miners can evaluate parent and child fees together.
mempool · fee · transaction
Replace By Fee (RBF)
→A mempool policy that can accept a conflicting unconfirmed transaction when the replacement satisfies fee and relay rules.
bitcoin · policy · fees
Package Relay
→The ability for nodes to relay groups of related transactions together so miners evaluate fees on the package total.
mempool · policy
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