CVE-2026-42770Network attack vector

Private-key recovery via attacker-supplied subgroup order

Published Jun 9, 2026 · Updated Jun 9, 2026

Missing DHX peer validation in affected OpenSSL releases allows remote attackers to recover static private keys via crafted X9.42 keys. EVP_PKEY_derive_set_peer() validates Y^q using the peer's q and compares p and g with the local key while failing to compare q, so forged small-order parameters confine the shared secret and reveal private-key residues. Affected versions are 3.0.0 through 3.0.20, 3.4.0 through 3.4.5, 3.5.0 through 3.5.6, 3.6.0 through 3.6.2, and 4.0.0; exposure requires interactive protocols with long-lived DHX keys, chiefly CMP RA or CA deployments and bespoke applications.

CVSS severity3.7
Low
EPSS probability0.47%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Missing DHX peer validation in affected OpenSSL releases allows remote attackers to recover static private keys via crafted X9.42 keys. EVP_PKEY_derive_set_peer() validates Y^q using the peer's q and compares p and g with the local key while failing to compare q, so forged small-order parameters confine the shared secret and reveal private-key residues. Affected versions are 3.0.0 through 3.0.20, 3.4.0 through 3.4.5, 3.5.0 through 3.5.6, 3.6.0 through 3.6.2, and 4.0.0; exposure requires interactive protocols with long-lived DHX keys, chiefly CMP RA or CA deployments and bespoke applications.

The record

CVE
CVE-2026-42770
Published
Jun 9, 2026
Updated
Jun 9, 2026
Vendor
OpenSSL Project
Product
OpenSSL
Classifications
CWE-325
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 9, 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=3.0.0 <3.0.21
  2. Affected versionversion=3.4.0 <3.4.6
  3. Affected versionversion=3.5.0 <3.5.7
  4. Affected versionversion=3.6.0 <3.6.3
  5. Affected versionversion=4.0.0 <4.0.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OpenSSL Project · OpenSSLversion=3.0.0 <3.0.21; version=3.4.0 <3.4.6; version=3.5.0 <3.5.7; version=3.6.0 <3.6.3; version=4.0.0 <4.0.1

Published CVSS scores

3.7CISA-ADPCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

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.

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

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-325Missing Cryptographic Step

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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