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MalwarePublished Updated

bytecore (npm) · Malicious Code

Affects bytecoreSource GCVE Database

0

Malicious package : remove bytecore and rotate any secrets on hosts that installed it.

Data as of 7 Jul 2026, 12:28 UTC

Classification

Malicious package

Published to npm · OSV MAL-2026-4503

What to do

Remove bytecore from every project, lockfile and image that pulls it in. Treat any host that installed it as compromised: rotate the credentials, tokens and keys it could read, from a clean machine.

Affected software

ProductAffectedFixed in
npmbytecoreAffected
  • =5.3.1
Fixed in–

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Description

--- _-= Per source details. Do not edit below this line.=-_ ## Source: amazon-inspector (1c1ddd2dea35052822d2dc89f0f46ceae20c772c257e0c97f0024483e9ff31c0) The package masquerades as a pino-like logging middleware (README is copied from pino, exports a `pino` property, mimics pino's option shape) but the middleware factory in index.js spawns a detached `node lib/caller.js` child process when the exported function is invoked. lib/caller.js obfuscates a hardcoded C2 URL by shadowing the real `process` global with a local object whose `env` holds base64-encoded strings; decoding `DEV_API_KEY` yields `https://jsonkeeper.com/b/BADC6`. The script GETs that anonymous, mutable paste host with axios (retried 5 times) and passes the response body to `new Function.constructor("require", s)(require)`, executing attacker-controlled JavaScript with full Node privileges and direct access to `require`. Any application that installs bytecore and mounts the middleware (`app.use(require('bytecore')())`) runs whatever code the paste currently serves. The combination of (a) mutable anonymous paste host as code source, (b) `require`-passing eval of fetched bytes, (c) base64 + process-shadowing obfuscation of the C2, and (d) impersonation of a popular logger to lure installers is an unambiguous remote-code-execution backdoor. ## Source: ghsa-malware (50cd544442497b8b42cd0b27eef33c15e4d0ff4a14c490183664f8cd0a795ef2) 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.

References

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