Timing Side-Channel in SM2 Signature Generation

Answer in brief

CVE-2026-77696 records a Low severity (CVSS 3.7) vulnerability in Timing Side-Channel in SM2 Signature Generation. The current sources do not mark it as known exploited. The current feed maps OpenSSL/OpenSSL (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 29, 2026Updated Sep 29, 2026Source checked Sep 29, 2026First seen by HOL Sep 29, 2026Material review Sep 29, 2026

Upstream Advisory

Key facts

Risk: Low · CVSS 3.7
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 3.7. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps OpenSSL/OpenSSL (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
OpenSSL/OpenSSLgeneric	>=4.0.0 <4.0.3 \|\| >=3.6.0 <3.6.5 \|\| >=3.5.0 <3.5.9 \|\| >=3.4.0 <3.4.8 \|\| >=3.0.0 <3.0.23 \|\| >=1.1.1 <1.1.1zj	4.0.3, 3.6.5, 3.5.9, 3.4.8, 3.0.23, 1.1.1zj

Recommended response

Check inventory. Check lockfiles and deployed manifests for OpenSSL/OpenSSL.
Review the reported fix. Update OpenSSL/OpenSSL to 4.0.3 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 29, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 29, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 29, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.