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CVE-2026-73567: sm-crypto: Predictable SM2 key generation in Node.js: default RNG uses Math.random + wall clock

• Severity: critical (CVSS 9.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-13 · updated 2026-10-24
• Weakness: CWE-338

Description

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.

Affected products

• JuneAndGreen sm-crypto: before 0.5.0

References

• https://github.com/JuneAndGreen/sm-crypto/commit/1f9bd7bd160c24efd9c26c8f7fda997c68c823d0
• https://github.com/JuneAndGreen/sm-crypto/security/advisories/GHSA-vh45-f885-3848

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