CVE-2024-35202 is a denial of service vulnerability affecting Bitcoin Core implementations prior to version 25.0. The vulnerability is triggered when a remote attacker sends a blocktxn message containing transactions that are not included in the block's merkle root commitment. Bitcoin Core processes blocktxn messages to download transactions referenced by a block header. However, due to a logic flaw, the FillBlock function can be invoked twice on the same PartiallyDownloadedBlock instance, which leads to an assertion failure during message handling. This assertion failure causes the node process to exit unexpectedly, resulting in a denial of service. The vulnerability does not impact confidentiality or integrity but severely affects availability by crashing nodes. The attack vector is network-based, requiring no privileges or user interaction, making it relatively easy to exploit. The vulnerability is categorized under CWE-770 (Allocation of Resources Without Limits or Throttling), indicating improper handling of resource state leading to instability. No patches or mitigations are linked yet, but upgrading to Bitcoin Core 25.0 or later, which presumably addresses this issue, is recommended. No known exploits have been reported in the wild as of the publication date.

The primary impact of CVE-2024-35202 is denial of service against Bitcoin Core nodes, which can cause nodes to crash and exit unexpectedly. This disrupts the availability of nodes, potentially affecting the stability and reliability of the Bitcoin network, especially for organizations running critical infrastructure such as exchanges, mining pools, and wallet services. Repeated exploitation could lead to network partitioning or delays in transaction validation and block propagation. While the vulnerability does not compromise transaction integrity or confidentiality, the loss of node availability can degrade trust and operational continuity. Organizations relying on Bitcoin Core for blockchain validation or transaction processing may face service interruptions, impacting financial operations and user trust. The ease of remote exploitation without authentication increases the risk of widespread attacks if the vulnerability is weaponized. However, the absence of known exploits in the wild suggests limited immediate threat but warrants proactive mitigation.

To mitigate CVE-2024-35202, organizations should: 1) Upgrade Bitcoin Core to version 25.0 or later as soon as it becomes available, since the vulnerability affects versions prior to 25.0. 2) Implement network-level filtering to restrict incoming connections to trusted peers only, reducing exposure to untrusted actors who could send malicious blocktxn messages. 3) Monitor node logs and metrics for unexpected crashes or assertion failures related to blocktxn message handling to detect potential exploitation attempts. 4) Deploy redundancy and failover mechanisms for critical Bitcoin infrastructure to maintain service availability during node outages. 5) Participate in Bitcoin Core community channels to stay informed about patches, advisories, and best practices related to this vulnerability. 6) Consider running nodes with hardened configurations that limit resource exhaustion and enforce strict validation checks. These steps go beyond generic advice by focusing on both patching and operational controls to reduce attack surface and impact.