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Malicious code in base65-13x (npm)

Malware Published Aug 11, 2026 to the GitHub Advisory Database • Updated Aug 11, 2026

Package

npm base65-13x (npm)

Affected versions

= 5.0.2

Patched versions

None

Description

Source: amazon-inspector (59226f2c38efcc1dd5de6423edfc866125564cd726915307d7a05ca5b5f13529)

base65-13x@5.0.2 impersonates cryptocoinjs/base-x, reusing its README, homepage, and API surface, but the exported decode(string) function in both src/esm/index.js (line 114) and src/cjs/index.cjs (line 116) contains a ~123KB VM-style obfuscated payload using rotated identifiers (vmR, vmr_92f1a9, vmw_4ee781) built via Object.defineProperty. The blob contains multiple references to the Function constructor and fetch, indicating dynamic code construction and outbound network I/O. Genuine base-x is roughly 50 lines of pure arithmetic with no obfuscation and no network activity. Any consumer invoking decode() on this package executes the packed VM, which dynamically constructs code with fetch capability. The destination hosts and constructed code are concealed by the obfuscation and are not statically visible.


Credit: OpenSSF (source)

References

Published to the GitHub Advisory Database Aug 11, 2026
Reviewed Aug 11, 2026
Last updated Aug 11, 2026

EPSS score

Weaknesses

Embedded Malicious Code

The product contains code that appears to be malicious in nature. Learn more on MITRE.

GHSA ID

GHSA-pm9q-qccp-rj4g

Source code

No known source code
Improvements are not currently accepted on this advisory because this package is malware and has no patched versions. If there is something to change, please open an issue at https://github.com/github/advisory-database/issues.