CVE-2026-18257Network attack vector

Authentication bypass via unchecked root expiration

Published Jul 29, 2026 · Updated Jul 29, 2026

Certificate validation in Systerel S2OPC 1.5.0 through 1.x allows remote attackers to establish trust via an expired root CA. The CycloneCrypto crt_verify_chain() root-end path accepts a trusted root's profile and trust status without checking its validity period. A remote party with a still-valid leaf certificate chained to an expired root that remains in the trust list can be authenticated by affected clients or servers.

CVSS severityUnavailable
Unscored
EPSS probability0.10%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Certificate validation in Systerel S2OPC 1.5.0 through 1.x allows remote attackers to establish trust via an expired root CA. The CycloneCrypto crt_verify_chain() root-end path accepts a trusted root's profile and trust status without checking its validity period. A remote party with a still-valid leaf certificate chained to an expired root that remains in the trust list can be authenticated by affected clients or servers.

The record

CVE
CVE-2026-18257
Published
Jul 29, 2026
Updated
Jul 29, 2026
Vendor
Systerel
Product
S2OPC
Classifications
T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 29, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 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=1.5.0 <2.0.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Systerel · S2OPCversion=1.5.0 <2.0.0

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.

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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

T1190Exploit Public-Facing Application

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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