Critical Vulnerabilities in Bitcoin Core: Risks of Outdated Node Software and the Path to Enhanced Security

BY KEYHUNTER 03.04.2025

Bitcoin Core developers have disclosed vulnerabilities in older software versions that affect approximately 6% of active Bitcoin nodes. These vulnerabilities, fixed in newer releases, include risks such as censorship of unconfirmed transactions, denial-of-service (DoS) attacks, and memory-related crashes. The most widespread flaw impacts nodes running versions prior to 0.21.0, potentially affecting 787 nodes. Other vulnerabilities include issues like remote code execution and CPU/memory DoS attacks, though these affect fewer nodes.

To address these concerns, Bitcoin Core developers have implemented a new security disclosure policy. This policy categorizes vulnerabilities into four severity levels—low, medium, high, and critical—and sets timelines for disclosure based on severity. Low-severity bugs will be disclosed shortly after fixes are released, while medium and high-severity bugs will be disclosed after the last affected version reaches its end-of-life. Critical bugs will follow an ad-hoc disclosure procedure.

The policy aims to improve transparency and incentivize responsible vulnerability reporting by researchers. It also seeks to encourage node operators to update their software regularly to enhance the network’s security and resilience. Vulnerabilities fixed in versions 0.21.0 and earlier are being disclosed immediately, with disclosures for subsequent versions planned over the coming months.

Summary

Around 6% of Bitcoin nodes are vulnerable due to outdated software versions, exposing them to risks like transaction censorship and DoS attacks. Bitcoin Core developers have introduced a new security disclosure policy to improve transparency and encourage updates, aiming to strengthen the network’s overall security. Node operators are advised to upgrade their software promptly to mitigate these risks[1][2].

A widespread node crash on the Bitcoin network could have several potential consequences, depending on the scale and nature of the crash:

1. Reduced Network Security

  • Nodes play a critical role in validating transactions and maintaining the blockchain’s integrity. A significant reduction in active nodes could weaken the network’s security, making it more susceptible to attacks such as double-spending or manipulation by malicious actors[4][6].

2. Risk of Chain Splits

  • If a large number of nodes crash simultaneously, it could lead to chain splits where different parts of the network disagree on the state of the blockchain. This can result in confusion, loss of trust, and potential financial losses for users[4].

3. Slower Transaction Processing

  • With fewer nodes available to validate transactions, processing times could increase significantly. This would reduce the efficiency of the network and impact user experience, especially during high transaction volumes[1][4].

4. Vulnerability to 51% Attacks

  • A node crash could concentrate mining power among fewer participants, increasing the risk of a 51% attack. In such an attack, a malicious entity controlling over half of the network’s mining power could rewrite parts of the blockchain and compromise its integrity[6].

5. Loss of Decentralization

  • Decentralization is a cornerstone of Bitcoin’s resilience. A widespread node crash might centralize control in fewer hands, undermining the principle of decentralization and making the network more vulnerable to systemic risks[1][4].

6. Economic Disruption

  • Bitcoin’s value is tied to its perceived security and reliability. A major node crash could shake investor confidence, leading to price volatility and broader economic repercussions within the cryptocurrency ecosystem[3][5].

While Bitcoin’s decentralized design provides some resilience against localized disruptions, a global or widespread node crash would pose significant challenges to its functionality and security.

Node operators can ensure their nodes are updated to the latest version by following these steps:

1. Use Node Version Manager (NVM)

  • Install NVM: Download and install NVM using the appropriate command for your operating system (e.g., curl or wget)[1][3].
  • Check Current Version: Use nvm ls to list installed versions or nvm ls-remote to view available releases[3].
  • Update Node: Install the latest version with nvm install node. You can switch between versions using nvm use [version_number][1][3].

2. Use Node.js Installer

  • Download Installer: Visit the official Node.js website and download the latest stable (LTS) or current version[3].
  • Run Installer: Follow the setup wizard to overwrite the older version with the new one[3].
  • Verify Update: Check the installed version using node -v[3].

3. Update via Package Managers

  • On macOS, use Homebrew: Run brew update && brew upgrade node.
  • On Linux, use the system’s package manager (e.g., sudo apt update && sudo apt install nodejs)[1][3].

4. Auto-Upgrading Nodes

For automated environments like Kubernetes, enable auto-upgrades to ensure nodes stay updated without manual intervention[5].

5. Update NPM

Since NPM is bundled with Node.js, it often updates automatically. If needed, update manually using:

npm install -g npm@latest

.

By regularly updating their software, node operators can improve security, performance, and compatibility with newer features.

Citations:
[1] https://www.geeksforgeeks.org/update-node-js-and-npm-to-latest-version/
[2] https://www.freecodecamp.org/news/how-to-update-node-and-npm-to-the-latest-version/
[3] https://phoenixnap.com/kb/update-node-js-version
[4] https://blog.hubspot.com/website/update-node-js
[5] https://cloud.google.com/kubernetes-engine/docs/how-to/node-auto-upgrades
[6] https://www.netguru.com/blog/update-node-js-version
[7] https://docs.npmjs.com/try-the-latest-stable-version-of-node/
[8] https://www.stackhawk.com/blog/managing-node-and-npm-versions-in-our-projects-best-practices-for-developers/

Citations:
[1] https://cointelegraph.com/news/can-internet-outages-really-disrupt-crypto-networks
[2] https://www.investopedia.com/tech/bitcoin-lightning-network-problems/
[3] https://originstamp.com/blog/what-happens-if-bitcoin-crashes-to-zero/
[4] https://cointelegraph.com/news/inflation-bug-still-a-danger-to-more-than-half-of-all-bitcoin-full-nodes
[5] https://www.investopedia.com/news/what-happens-if-bitcoin-price-crashes/
[6] https://www.investopedia.com/terms/1/51-attack.asp

Citations:
[1] https://cryptoslate.com/6-of-bitcoin-nodes-running-outdated-software-vulnerable-to-exploits/
[2] https://cryptobriefing.com/bitcoin-core-disclosure-policy/
[3] https://en.bitcoinsistemi.com/bitcoin-developers-detected-a-serious-vulnerability-these-should-be-done/
[4] https://protos.com/no-auto-update-in-bitcoin-core-means-13-of-nodes-could-crash/
[5] https://thenextweb.com/news/bitcoin-100000-nodes-vulnerable-cryptocurrency
[6] https://www.cointribune.com/en/bitcoin-over-2500-nodes-vulnerable-to-a-critical-bug/
[7] https://www.techrepublic.com/article/pentagon-finds-concerning-vulnerabilities-on-blockchain/
[8] https://protos.com/bitcoin-devs-finally-admitting-to-major-mistakes-in-core-software/