CVE-2026-77696
Timing Side-Channel in SM2 Signature Generation
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.
Fixes and workarounds
Fix
The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.
Source: CNA: opensslFix
The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.
Source: CNA: opensslFix
The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.
Source: CNA: opensslFix
The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.
Source: CNA: opensslAffected products and versions
| Product | Versions | Authority |
|---|---|---|
| OpenSSL OpenSSL |
≥ 4.0.0; < 4.0.3 (affected, semver) ≥ 3.6.0; < 3.6.5 (affected, semver) ≥ 3.5.0; < 3.5.9 (affected, semver) ≥ 3.4.0; < 3.4.8 (affected, semver) ≥ 3.0.0; < 3.0.23 (affected, semver) ≥ 1.1.1; < 1.1.1zj (affected, custom) Other versions: unaffected |
CNA: openssl |
| SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) Siemens |
≥ V3.1.7; < * (affected, custom)
Other versions: unknown |
ADP: siemens-SADP |
| SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) Siemens |
≥ V3.1.7; < * (affected, custom)
Other versions: unknown |
ADP: siemens-SADP |
| SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) Siemens |
≥ V3.1.7; < * (affected, custom)
Other versions: unknown |
ADP: siemens-SADP |
| SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) Siemens |
≥ V3.1.7; < * (affected, custom)
Other versions: unknown |
ADP: siemens-SADP |
| SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) Siemens |
≥ V3.1.7; < * (affected, custom)
Other versions: unknown |
ADP: siemens-SADP |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 3.1 / 3.7 low |
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N | ADP: CISA-ADP |
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://openssl-library.org/news/secadv/20260929.txtCNA: openssl · vendor-advisory
- https://github.com/openssl/openssl/commit/20b20628d39b2dcc4677194bd68c7c060fa598cbCNA: openssl · patch
- https://github.com/openssl/openssl/commit/1c4aed808a7aea32d2d013049c2e0d9fef164fc9CNA: openssl · patch
- https://github.com/openssl/openssl/commit/6b90445a56b99a328ac1feba058abf976504f440CNA: openssl · patch
- https://github.com/openssl/openssl/commit/419f5cb519721dceed393dbc524d79e487c72e64CNA: openssl · patch
- https://cert-portal.siemens.com/productcert/html/ssa-457936.htmlADP: siemens-SADP
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