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

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• 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.

From the GitHub advisory

Summary

CryptoJS.lib.WordArray.random() in affected versions is not a cryptographically secure random number generator. Nominal requests for 128 or 256 bits of entropy produce effective search spaces of approximately 2^39 and 2^47 possibilities — small enough to enumerate on commodity hardware.

Coinspect's Ill Bloom investigation confirmed that downstream wallet applications used this function as the entropy source for BIP39 recovery phrases.

An application is affected only if it uses the vulnerable function to generate security-sensitive values.

Merely depending on crypto-js

Weakness type: CWE-331, CWE-334, CWE-338.

Product: crypto-js (npm) · Assigned by: GitHub_M · Published: 2026-08-07

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: high (needs special conditions)
• Privileges required: none (no login)
• User interaction: none
• Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• 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.

Timeline

• 2026-08-07 — CVE record published by GitHub_M
• 2026-08-07 — GitHub-reviewed advisory GHSA-rg76-677x-56q9 published (critical)
• 2026-08-08 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-rg76-677x-56q9 github.com
2. CVE.org record CVE-2026-71851 cve.org
3. NVD entry CVE-2026-71851 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. coinspect.com coinspect.com

Critical npm advisories · Today’s Security Digest