EUVD-2026-352838

fkie_cve-2026-73567

sm-crypto provides JavaScript implementations of the Chinese cryptographic algorithms SM2, SM3, and SM4. Prior to 0.5.0, the default no-argument sm2.generateKeyPairHex() path in Node.js uses the module-wide SecureRandom instance in src/sm2/utils.js, supplied by jsbn@1.1.0, which seeds an ARC4 stream from Math.random() and new Date().getTime() because window.crypto.getRandomValues is unavailable even though globalThis.crypto exists. An attacker who can observe the process's Math.random() outputs and estimate the key-generation time can reconstruct the seed, recover generated SM2 private keys, and predict signing ephemeral scalars used to forge signatures. This issue is fixed in version 0.5.0.

GHSA-vh45-f885-3848 — sm-crypto: Predictable SM2 key generation in Node.js: default RNG uses Math.random + wall clock

Affected: npm: sm-crypto

## Summary

`sm-crypto` (npm package **0.4.0**, the latest release, published 2026-01-20) generates SM2 private keys and signing ephemeral scalars from a single module-wide RNG instance (`src/sm2/utils.js`: `const rng = new SecureRandom()`). `SecureRandom` is jsbn's PRNG, which seeds an **ARC4** stream from `window.crypto.getRandomValues` when available. **In Node.js — sm-crypto's primary runtime — `window` is `undefined`, so the CSPRNG branch is skipped** and the seed pool is instead filled from `Math.random()` (V8 `xorshift128+`, recoverable from a few outputs) plus `new Date().getTime()` (wall clock, attacker-estimable).

Node *does* expose Web Crypto as `globalThis.crypto`, but jsbn checks `window.crypto`, not `globalThis.crypto`, so the secure path is never taken. Consequently every SM2 private key produced by the default `sm2.generateKeyPairHex()` and every signing ephemeral scalar is derived from non-cryptographic sources and is **predictable** by an attacker who can observe a few `Math.random()` outputs and estimate the generation time.

This is the library's **default** (no-argument) path; no caller-selected parameter or configuration is required to trigger it. It is reproduced end-to-end against the unmodified real npm packages (`sm-crypto@0.4.0` + `jsbn@1.1.0`); the PoC below runs against the real installed package, not a copy. The defect is still present on the latest published version (0.4.0) and is not covered by any existing `JuneAndGreen/sm-crypto` issue (0 a…

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EUVD-2026-352838

fkie_cve-2026-73567

GHSA-vh45-f885-3848 — sm-crypto: Predictable SM2 key generation in Node.js: default RNG uses Math.random + wall clock