CVE-2026-77696

/// Technical description

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.

/// Remediation

Check the references section for vendor advisories and patches from openssl. Update openssl to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// Affected products

/// References