CVE-2024-55563 in Bitcoin
Summary
by MITRE • 12/09/2024
Bitcoin Core through 27.2 allows transaction-relay jamming via an off-chain protocol attack, a related issue to CVE-2024-52913. For example, the outcome of an HTLC (Hashed Timelock Contract) can be changed because a flood of transaction traffic prevents propagation of certain Lightning channel transactions.
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Analysis
by VulDB Data Team • 06/22/2025
The vulnerability identified as CVE-2024-55563 represents a significant weakness in the Bitcoin Core software ecosystem that specifically targets the transaction relay mechanism within the Bitcoin network. This flaw enables attackers to perform transaction-relay jamming through off-chain protocol attacks, creating a cascading effect that disrupts normal network operations and compromises the reliability of Bitcoin's payment infrastructure. The issue manifests when malicious actors exploit the network's transaction propagation system to flood the network with excessive transaction traffic, effectively preventing legitimate transactions from reaching their intended recipients within the Lightning Network protocol. The vulnerability is particularly concerning as it directly impacts the core functionality of Bitcoin's second-layer scaling solutions, which depend on reliable transaction propagation for their operation.
The technical implementation of this vulnerability stems from how Bitcoin Core handles transaction relay prioritization and network congestion management. When an attacker introduces a flood of transaction traffic, the network's existing mechanisms for determining which transactions should be propagated take precedence over legitimate channel update transactions. This creates a scenario where critical Lightning Network operations become delayed or blocked entirely, as the network becomes overwhelmed with lower-priority transactions that are designed to disrupt the normal flow of information. The vulnerability operates at the protocol level, specifically targeting the transaction relay policies that govern how nodes communicate transaction information to their peers, effectively creating a denial-of-service condition that affects the entire network infrastructure.
The operational impact of CVE-2024-55563 extends far beyond simple network disruption, fundamentally compromising the trust and reliability that users place in Bitcoin's payment infrastructure. When HTLC transactions are prevented from propagating properly, Lightning Network channels become unusable, causing financial losses for users who depend on these fast payment channels for their transactions. This vulnerability directly affects the Lightning Network's core functionality, where the timely propagation of channel updates is essential for maintaining channel liquidity and enabling secure cross-channel payments. The attack vector essentially creates a race condition where malicious transactions can prevent legitimate ones from completing, leading to channel failures and potential fund losses for participants in the Bitcoin ecosystem.
This vulnerability aligns with several established cybersecurity frameworks and attack patterns, particularly those related to network-level denial-of-service attacks and protocol manipulation. From a CWE perspective, this issue demonstrates characteristics of CWE-400: Uncontrolled Resource Consumption and CWE-310: Cryptographic Issues, as it involves both resource exhaustion through transaction flooding and the manipulation of cryptographic transaction relationships within the Bitcoin protocol. The attack methodology also corresponds to ATT&CK technique T1498: Network Denial of Service, where the adversary leverages the network's own protocols against itself to create operational disruption. Additionally, this vulnerability highlights the importance of proper resource management and priority queuing in distributed systems, as it demonstrates how a single protocol flaw can cascade through an entire network infrastructure.
Mitigation strategies for CVE-2024-55563 require both immediate patching and architectural improvements to the transaction relay mechanisms within Bitcoin Core. The most direct solution involves updating to Bitcoin Core versions that have implemented proper transaction relay prioritization and rate-limiting mechanisms to prevent malicious transaction flooding from disrupting legitimate network operations. Network operators should implement additional monitoring systems to detect unusual transaction traffic patterns that may indicate attempted attacks, while also configuring their nodes to prioritize critical transactions over low-priority ones. The implementation of more sophisticated transaction filtering and relay policies can help ensure that Lightning Network channel updates maintain their priority in network propagation, preventing the cascading failures that occur when legitimate transactions are blocked by malicious traffic. Organizations using Bitcoin infrastructure should also consider implementing transaction whitelisting mechanisms and enhanced node configuration settings to protect against this specific class of attack while maintaining network connectivity and performance standards.