---
title: "CVE-2026-71851: crypto-js: Insufficient Entropy in Cryptographic Secret Generation via Vulnerable CryptoJS Dependency Chain"
url: https://erroneo.us/security/cve/CVE-2026-71851/
description: "CVE-2026-71851 (crypto-js (npm)): crypto-js is a JavaScript library of crypto standards. Versions of crypto-js prior to 4.0.0 generate randomness in…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-08-07
date_modified: 2026-08-08
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-71851"
kev: false
cvss: 9
epss: 0.0055
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-71851: crypto-js: Insufficient Entropy in Cryptographic Secret Generation via Vulnerable CryptoJS Dependency Chain

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.5% , percentile 45: FIRST’s model estimates a 0.5% chance of exploitation activity in the next 30 days, higher than 45% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes crypto-js (npm) < 4.0.0, fixed in 4.0.0 . Check your lockfile, including transitive dependencies.

## What it is

crypto-js is a JavaScript library of crypto standards. Versions of crypto-js prior to 4.0.0 generate randomness in CryptoJS.lib.WordArray.random() using a custom variation of the Multiply-With-Carry pseudorandom number generator, seeded from Math.random(), instead of a cryptographically secure source. This generator was introduced in version 3.1.2-4 and remained present in nearly every 3.x release. Nominal requests for 128 or 256 bits of entropy through this function produce effective search spaces of approximately 2 to the 39th and 2 to the 47th possibilities, small enough to enumerate on commodity hardware. Downstream wallet applications that used CryptoJS.lib.WordArray.random() as the entropy source for BIP39 recovery phrases are affected, and an attacker who enumerates the reduced output space can recover the resulting private keys and control the associated funds. This issue is fixed in version 4.0.0.

## Affected packages

- npm `crypto-js` < 4.0.0 → fixed: 4.0.0

## Affected products (CVE record)

- brix crypto-js: < 4.0.0

## Severity

- GitHub_M CVSS 3.1: 9 `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H`
- GitHub CVSS 3.1: 9.0 `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable no , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.55% probability of exploitation activity in the next 30 days; percentile 45.

## Sources

- [GitHub Advisory GHSA-rg76-677x-56q9](https://github.com/advisories/GHSA-rg76-677x-56q9)
- [CVE.org record CVE-2026-71851](https://www.cve.org/CVERecord?id=CVE-2026-71851)
- [NVD entry CVE-2026-71851](https://nvd.nist.gov/vuln/detail/CVE-2026-71851)
- [github.com](https://github.com/brix/crypto-js/security/advisories/GHSA-rg76-677x-56q9)
- [github.com](https://github.com/brix/crypto-js/commit/b405ff597fb3ac76a7bdfbc72dca10ba1079b1d5)
- [coinspect.com](https://www.coinspect.com/blog/ill-bloom-investigation)

---
Source page: https://erroneo.us/security/cve/CVE-2026-71851/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt