Detection rules › Sigma
Shai-Hulud Malicious Bun Execution
Detects the execution of bun_environment.js via the Bun runtime, a behavior associated with the Shai-Hulud "Second Coming" NPM supply chain attack. The malware uses a setup_bun.js script to install the Bun runtime if not present, and then executes the malicious bun_environment.js payload.
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Initial Access | T1195.002 Supply Chain Compromise: Compromise Software Supply Chain |
| Execution | T1203 Exploitation for Client Execution |
Event coverage
| Provider | Event | Title |
|---|---|---|
| Sysmon | Event ID 1 | Process creation |
| Security-Auditing | Event ID 4688 | A new process has been created. |
Rule body yaml
title: Shai-Hulud Malicious Bun Execution
id: 5299fadf-f228-4526-8274-251db1960be9
related:
- id: eb827bbd-670a-4d58-8446-c464d8ac2323
type: similar
status: experimental
description: |
Detects the execution of `bun_environment.js` via the Bun runtime, a behavior associated with the Shai-Hulud "Second Coming" NPM supply chain attack.
The malware uses a `setup_bun.js` script to install the Bun runtime if not present, and then executes the malicious `bun_environment.js` payload.
references:
- https://www.aikido.dev/blog/shai-hulud-strikes-again-hitting-zapier-ensdomains
- https://www.wiz.io/blog/shai-hulud-2-0-ongoing-supply-chain-attack
- https://github.com/asyncapi/cli/blob/2efa4dff59bc3d3cecdf897ccf178f99b115d63d/setup_bun.js
- https://semgrep.dev/blog/2025/digging-for-secrets-sha1-hulud-the-second-coming-of-the-npm-worm/
author: Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2025-11-25
tags:
- attack.t1195.002
- attack.t1203
- attack.execution
- attack.initial-access
- detection.emerging-threats
logsource:
category: process_creation
product: windows
detection:
selection_parent:
ParentImage|endswith: '\node.exe'
selection_child_bun_script:
Image|endswith: '\bun.exe'
CommandLine|contains:
- 'bun_environment.js'
- 'https://github.com/actions/runner/releases/download/v2.330.0'
condition: selection_parent and 1 of selection_child_*
falsepositives:
- Legitimate but uncommon use of files named `bun_environment.js` could trigger this rule.
level: high
regression_tests_path: regression_data/rules-emerging-threats/2025/Malware/Shai-Hulud/proc_creation_win_mal_shai_hulud_malicious_node_bun_execution/info.yml
Stages and Predicates
Stage 0: condition
selection_parent and 1 of selection_child_*Stage 1: selection_parent
selection_parent:
ParentImage|endswith: '\node.exe'
Stage 2: selection_child_bun_script
selection_child_bun_script:
Image|endswith: '\bun.exe'
CommandLine|contains:
- 'bun_environment.js'
- 'https://github.com/actions/runner/releases/download/v2.330.0'
Indicators
Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.
| Field | Kind | Values |
|---|---|---|
CommandLine | match |
|
Image | ends_with |
|
ParentImage | ends_with |
|