SM2-PKE has 32-bit Biased Nonce Vulnerability

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.7 · 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 · score source

EPSS

• CVE-2026-22698: 0.27% estimated exploitation activity in the next 30 days; percentile 19.89 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary 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. Affected Versions - sm2 0.14.0-rc.0 (https://crates.io/crates/sm2/0.14.0-rc.0) - sm2 0.14.0-pre.0 (https://crates.io/crates/sm2/0.14.0-pre.0) This vulnerability is introduced in commit: Commit 4781762 on Sep 6, 2024, which is over a year ago. Details The root cause of this vulnerability is a unit mismatch in the encrypt function located in sm2/src/pke/encrypting.rs. 1. The code correctly calculates the byte-length of the curve order (256 bits / 8 = 32 bytes) and stores it in a…

Published by the source

9 Jan 2026, 22:27 UTC

Last modified by the source

11 Jan 2026, 14:56 UTC

Source last checked

26 Oct 2026, 15:39 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-w3g8-fp6j-wvqw

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# Patch Next advisory brief: CVE-2026-22698

Advisory: SM2-PKE has 32-bit Biased Nonce Vulnerability
IDs: CVE-2026-22698, GHSA-w3g8-fp6j-wvqw
Record: https://patchnext.com/advisories/cve-2026-22698 (revision 1, source checked 26 Oct 2026, 15:39 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io sm2: affected >= 0.14.0-pre.0, <= 0.14.0-rc.4

## Suggested inspection (read-only)
- crates.io sm2: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on sm2.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-w3g8-fp6j-wvqw (GitHub-reviewed advisory GHSA-w3g8-fp6j-wvqw lists affected ranges: crates.io sm2 >=0.14.0-pre.0 <=0.14.0-rc.4)

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