Low · published September 29, 2026
Issue summary: SM2 signature generation uses non-constant-time arithmetic
on secret values, forming a timing side-channel.
Impact summary: An attacker able to measure SM2 signing times may learn
information about the per-signature secret nonce, which over many signatures
can, via a lattice / Hidden Number Problem attack, lead to recovery of the
private key.
CWE: CWE-208: Observable Timing Discrepancy
Description: SM2 signature generation computes the signature value using
variable-time BIGNUM operations on the secret nonce and the private key, so
the time taken to produce an SM2 signature depends on these secret values,
forming a timing side-channel.
Applications performing SM2 signature generation are affected on all
platforms.
FIPS Impact: no
SM2 is not a FIPS algorithm.
| Product | Versions | Fixed in |
|---|---|---|
| openssl/openssl | ≥ 1.1.1, < 1.1.1zj | 1.1.1zj |
| openssl/openssl | ≥ 3.0.0, < 3.0.23 | 3.0.23 |
| openssl/openssl | ≥ 3.4.0, < 3.4.8 | 3.4.8 |
| openssl/openssl | ≥ 3.5.0, < 3.5.9 | 3.5.9 |
| openssl/openssl | ≥ 3.6.0, < 3.6.5 | 3.6.5 |
| openssl/openssl | ≥ 4.0.0, < 4.0.3 | 4.0.3 |