npm

base65-11x @5.0.2

Vulnerability report · Last retrieved from osv.dev August 12, 2026 at 3:23 AM UTC

Malicious

OSV ID

MAL-2026-13745

Ecosystem

npm

Summary

base65-11x is a name-lookalike of the widely used base-x encoder. Both entrypoints (src/cjs/index.cjs and src/esm/index.js, ~127KB each vs. ~4KB for real base-x) contain the legitimate base-x source followed by a ~123KB single-line obfuscated payload wrapped in a custom-VM IIFE (identifiers vmN, vmA_ab9191, vmU_d6a896; Object.defineProperty-based dispatch on a global slot). The payload sits at module top level, so it executes automatically whenever a consumer require()s or import()s the package. A pure base-encoding utility has no functional need for runtime-VM-packed code on load, and the payload is duplicated across CJS and ESM entrypoints to ensure execution regardless of module system. The specific payload behavior is concealed inside the VM interpreter and cannot be recovered without executing it.

Source: amazon-inspector (14cc9506a804a2663d0cde1c610fa8cba5733e6797652b6365569ada5ef3901d)

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