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Vulnerability · Published Sep 29, 2026 · Assigned by openssl

CVE-2026-77696Timing Side-Channel in SM2 Signature Generation

Low 3.7

In plain English

A low-severity security flaw in OpenSSL from OpenSSL. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 34% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)3.7Low
Exploit odds (30 days)0.4%top 66.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Alpine:v3.21openssl3.3.7-r2ALPINE-CVE-2026-77696
Debian:12openssl3.0.22-1~deb12u2DEBIAN-CVE-2026-77696
Debian:13openssl3.5.7-1~deb13u3DEBIAN-CVE-2026-77696
Debian:14openssl3.6.5-1DEBIAN-CVE-2026-77696
Ubuntu:22.04:LTSedk2no fix listedUBUNTU-CVE-2026-77696
Ubuntu:24.04:LTSedk2no fix listedUBUNTU-CVE-2026-77696
Ubuntu:26.04:LTSedk2no fix listedUBUNTU-CVE-2026-77696
Ubuntu:26.10edk2no fix listedUBUNTU-CVE-2026-77696
Ubuntu:26.04:LTSedk2-hweno fix listedUBUNTU-CVE-2026-77696
Ubuntu:26.10edk2-hweno fix listedUBUNTU-CVE-2026-77696
Ubuntu:22.04:LTSopenssl3.0.2-0ubuntu1.30UBUNTU-CVE-2026-77696
Ubuntu:22.04:LTSopenssl3.0.2-0ubuntu1.30USN-8847-1
Ubuntu:24.04:LTSopenssl3.0.13-0ubuntu3.16UBUNTU-CVE-2026-77696
Ubuntu:24.04:LTSopenssl3.0.13-0ubuntu3.16USN-8847-1
Ubuntu:26.04:LTSopenssl3.5.5-1ubuntu3.6USN-8847-1
Ubuntu:26.04:LTSopenssl3.5.5-1ubuntu3.6UBUNTU-CVE-2026-77696

Affected products (as reported)

VendorProductVersions
OpenSSL OpenSSL 4.0.0 – before 4.0.33.6.0 – before 3.6.53.5.0 – before 3.5.93.4.0 – before 3.4.83.0.0 – before 3.0.231.1.1 – before 1.1.1zj

Weakness: CWE-208 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

References