Vulnerability in Bitcoin : CVE-2024-38365

 Vulnerability in Bitcoin : CVE-2024-38365

CVE-2024-38365 highlights a critical vulnerability in the btcd Bitcoin client, which is an alternative full node implementation of Bitcoin written in Go (Golang). This vulnerability affects btcd versions 0.10 to 0.24 and revolves around an incorrect re-implementation of Bitcoin Core's "FindAndDelete()" functionality. The implications of this flaw are significant, as it could lead to consensus failures within the Bitcoin network, potentially allowing attackers to exploit it for chain splits or denial-of-service (DoS) attacks against btcd nodes.

Technical Details

Consensus-Critical Logic

The "FindAndDelete()" function is crucial for maintaining consensus across Bitcoin clients. It is designed to remove specific data from scripts in transactions. However, the logic implemented in btcd differs from that in Bitcoin Core, leading to inconsistent behavior:

• FindAndDelete(): This function is supposed to remove exact matches from a script.
• removeOpCodeByData(): This function, on the other hand, removes data pushes that match a specified pattern.

For example, consider the following script:

text
script = "<data> <data||foo>"
dataToRemove = "data"

In this case:

• btcd would remove both occurrences of <data>.
• Bitcoin Core would only remove the first occurrence.

This discrepancy can lead to situations where btcd accepts an invalid block or rejects a valid one, thus creating a potential chain split.

Exploitation Potential

An attacker can exploit this vulnerability by crafting a standard transaction that causes FindAndDelete() not to return a match while removeOpCodeByData() does. This manipulation leads to different signature hashes (sighashes) being generated by btcd compared to other clients. Consequently, this could allow an attacker to:

1. Create a Chain Split: By making btcd accept an invalid block.
2. Execute DoS Attacks: By causing btcd nodes to reject valid blocks, leading them to be out of sync with the rest of the network.

Importantly, this vulnerability can be exploited remotely by any user on the Bitcoin network without requiring significant computational power or resources.

Mitigation and Resolution

The vulnerability was officially patched in btcd version v0.24.2, released shortly after its discovery on October 11, 2024. Users operating affected versions are strongly advised to upgrade their clients immediately to mitigate any risks associated with this vulnerability.

No Known Workarounds

There are currently no known workarounds for this issue. The only effective solution is upgrading to the patched version of btcd.

Conclusion

CVE-2024-38365 serves as a critical reminder of the importance of consensus mechanisms in blockchain technology and the potential risks associated with discrepancies in client implementations. The incident underscores the need for rigorous testing and adherence to established protocols within cryptocurrency software development. Users and developers alike must remain vigilant against such vulnerabilities to ensure the integrity and security of blockchain networks.

• https://nvd.nist.gov/vuln/detail/CVE-2024-38365