The ‘Miasma’ worm source code briefly leaked on GitHub

Summary

The source code for the Miasma credential-stealing malware, which targets open-source ecosystems via supply-chain attacks, was briefly leaked on GitHub. This malware, an evolution of the Shai-Hulud worm, infects developer machines, steals credentials, and uses them to compromise repositories and packages, propagating itself autonomously. The leak is expected to lead to more advanced variants and an increase in supply-chain attacks.

Full text

The ‘Miasma’ worm source code briefly leaked on GitHub By Bill Toulas June 10, 2026 04:27 PM 0 The Miasma credential-stealing attack framework, which has recently targeted open-source ecosystems through supply-chain attacks, was briefly open-sourced on GitHub. Miasma appears to be an evolution of the earlier Shai-Hulud worm, which was previously leaked on GitHub and shares much of the same features, techniques, and even code. The malware infects a developer machine, steals the build environment and cloud credentials, and then uses those to compromise legitimate repositories and packages, publishing trojanized versions to infect downstream developers and repeat the cycle. This autonomous, worm-like self-propagation mechanism can quickly expand its reach, potentially turning a single breach into a widespread supply chain attack. The malware has previously been linked to high-profile attacks against Red Hat npm packages and, more recently, 73 Microsoft repositories on GitHub. Researchers at SafeDep reported yesterday that the Miasma source code was leaked on GitHub via numerous compromised developer accounts. In each of those accounts, the threat actors leaked the source code in a repo named "Miasma-Open-Source-Release." This indicates that the threat actors deliberately released the source code, rather than it being an accidental leak, similar to how the Shai-Hulud code was published earlier. The published source code filesSource: SafeDep Analysis of the code showed that the toolkit requires no command-and-control (C2) infrastructure to operate, as it uses GitHub for that purpose. The framework harvests credentials from cloud providers, CI/CD systems, password managers, Kubernetes, and secret stores, and abuses them to compromise npm, PyPI, and RubyGems packages, as well as GitHub repositories, Actions workflows, and JFrog Artifactory instances. It can also move laterally through SSH and AWS Systems Manager (SSM), and poison configurations of AI coding tools such as Claude, Gemini, Cursor, Copilot, Kiro, and Cline. Architecture diagramSource: SafeDep One interesting feature revealed in the leaked Miasma source code is a "dead-man switch" that is installed when the malware uses a victim's stolen GitHub token as an exfiltration channel. The component monitors the token's validity every minute and, if it's revoked, executes a destructive command (rm -rf ~/; rm -rf ~/Documents), recursively deleting files and directories in the user's home and Documents folders. The monitor runs as a systemd user service on Linux or a LaunchAgent on macOS, and remains active for up to 72 hours. Another interesting aspect revealed is a five-stage build pipeline that generates unique payloads for each build. SafeDep reports that the process combines per-file AES-256-GCM encryption of embedded assets, randomized string obfuscation, source transformations, JavaScript obfuscation, and a self-extracting loader that wraps the final payload in three layers of encryption. Random keys and a randomized outer encoding layer ensure that each generated sample differs from previous builds, making signature-based detection and static analysis harder. The leak of Shai Hulud led to the release of more advanced variants, such as Miasma, and to increased attack rates. Similarly, the leak of Miasma's source code is expected to have a similar effect as threat actors adopt the code and further adjust it. This could have significant consequences for the security of the open-source ecosystem, as supply-chain attacks continue to target it at an unprecedented pace. Software developers are advised to pin project dependencies, introduce multi-day delays before adopting newly released package updates, and validate new builds in isolated test environments. Test every layer before attackers do Security teams log 54% of successful attacks and alert on just 14%. The rest move through your environment unseen.The Picus whitepaper shows how breach and attack simulation tests your SIEM and EDR rules so threats stop slipping by detection. Get the whitepaper Related Articles: New IronWorm malware hits 36 packages in npm supply-chain attackGitHub disables Microsoft repos pushing password-stealing malwareNew Shai-Hulud attack trojanizes 19 science-focused PyPI packagesRed Hat npm packages compromised to steal developer credentialsNew Shai-Hulud malware wave compromises 600 npm packages

Indicators of Compromise

• malware — Miasma
• malware — Shai-Hulud

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