{"answers":{"affected":"1 open source package ship an affected version, including bytecore.","exploited":"There is no known exploitation of MAL-2026-4503 in the wild and no public exploit code.","fix":"Remove the package from your dependencies and lockfiles, then rotate any secrets on machines where it was installed.","what":"MAL-2026-4503 is a malicious package in bytecore, published on 19 May 2026."},"fix_prompt":"MAL-2026-4503 is a malicious package: bytecore (npm). Every version was published to cause harm.\n\nTask:\n1. Search this repository's dependency manifests and lockfiles for the package, including transitive dependencies.\n2. If it is present, remove it, regenerate the lockfile with the project's package manager, and replace whatever it was used for.\n3. List any CI runners, developer machines or containers that installed it, so their secrets can be rotated.\n4. If the package is not used anywhere, say so and change nothing.\n\nReference: https://insights.sbomify.com/MAL-2026-4503/ (Markdown: https://insights.sbomify.com/MAL-2026-4503/index.md)","id":"MAL-2026-4503","markdown":"https://insights.sbomify.com/MAL-2026-4503/index.md","name":"MAL-2026-4503","record":{"aliases":["GHSA-x73m-hgh7-64q2"],"analysis":null,"analysis_generated_by":null,"assigner":null,"cpe":[],"cvss":{"score":null,"severity":null,"source":null,"vector":null,"version":null},"cwes":[],"description":"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.\n\nAny 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.","ecosystems":["npm"],"exploits":{"exploitdb":null,"first_seen":null,"github_poc":null,"max_poc_stars":null,"metasploit":null,"nuclei":null,"refs":[],"tier":null},"has_fix":false,"headline":"Malicious code in bytecore (npm)","id":"MAL-2026-4503","indexable":true,"kev":null,"kind":"malicious","links":{"ecosystem":"npm","product":null,"products":[],"type":null,"year":"2026"},"n_packages":1,"n_references":null,"packages":[{"ecosystem":"npm","fixed":[],"introduced":[],"last_affected":[],"package":"bytecore","purl":"pkg:npm/bytecore","source":"MAL-2026-4503"}],"products":null,"published":"2026-05-19","related":[],"sources":[{"class":"attribution","licence":"Apache-2.0","name":"OpenSSF Malicious Packages","prefix":"MAL"}],"ssvc":{"automatable":null,"exploitation":null,"technical_impact":null},"state":null,"updated":null,"vendors":null},"summary":null,"url":"https://insights.sbomify.com/MAL-2026-4503/"}