CVE-2026-77696: openssl Observable Timing Discrepancy

Vulnerability summary

CVE-2026-77696 is a low (CVSS 3.7) Observable Timing Discrepancy vulnerability in openssl. EPSS estimates a 0.24% chance of exploitation in the next 30 days, higher than 14.5% of scored vulnerabilities.

Timeline

1. 29-09-2026
   PublishedVulnerability first disclosed.
2. 29-09-2026
   Last modifiedVulnerability information updated.

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.

• CWE-208Observable Timing DiscrepancyTwo separate operations in a product require different amounts of time to complete, in a way that is observable to an actor and reveals security-relevant information about the state of the product, such as whether a particular operation was successful or not.