CVE-2026-77696Hinoki check available

Private-key recovery via variable-time SM2 signing

Published Sep 29, 2026 · Updated Sep 29, 2026

A timing side-channel in OpenSSL SM2 signing allows attackers to infer secret nonce data from repeated signing times. The sm2_sig_gen() path uses variable-time BIGNUM operations on the nonce and private key, making signature duration depend on secret values. Exploitation requires access to many timed SM2 signing operations; accumulated nonce information can enable private-key recovery through a lattice attack.

CVSS severityUnavailable
Unscored
EPSS probability0.24%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

A timing side-channel in OpenSSL SM2 signing allows attackers to infer secret nonce data from repeated signing times. The sm2_sig_gen() path uses variable-time BIGNUM operations on the nonce and private key, making signature duration depend on secret values. Exploitation requires access to many timed SM2 signing operations; accumulated nonce information can enable private-key recovery through a lattice attack.

The record

CVE
CVE-2026-77696
Published
Sep 29, 2026
Updated
Sep 29, 2026
Vendor
OpenSSL Project
Product
OpenSSL
Classifications
CWE-208
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Sep 29, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 29, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.1.1 <1.1.1zj
  2. Affected versionversion=3.0.0 <3.0.23
  3. Affected versionversion=3.4.0 <3.4.8
  4. Affected versionversion=3.5.0 <3.5.9
  5. Affected versionversion=3.6.0 <3.6.5
  6. Affected versionversion=4.0.0 <4.0.3

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

OpenSSL Project · OpenSSLversion=1.1.1 <1.1.1zj; version=3.0.0 <3.0.23; version=3.4.0 <3.4.8; version=3.5.0 <3.5.9; version=3.6.0 <3.6.5; version=4.0.0 <4.0.3

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-208Observable Timing Discrepancy

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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