CVE-2026-6899Network attack vector

Authentication bypass via first-match CRL validation

Published Jun 9, 2026 · Updated Jun 9, 2026

Certificate revocation bypass in Systerel S2OPC 1.5.0 through 1.7.2 allows remote attackers to connect with a revoked certificate. The crt_verifycrl_and_check_revocation function stops after the first valid CRL for a CA instead of checking every valid CRL, so a later revocation entry is ignored. Exposure requires the CycloneCrypto wrapper and multiple valid CRLs for the same CA; the result is an OPC UA connection that should be rejected.

CVSS severity5.6
Medium
EPSS probability0.11%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Certificate revocation bypass in Systerel S2OPC 1.5.0 through 1.7.2 allows remote attackers to connect with a revoked certificate. The crt_verifycrl_and_check_revocation function stops after the first valid CRL for a CA instead of checking every valid CRL, so a later revocation entry is ignored. Exposure requires the CycloneCrypto wrapper and multiple valid CRLs for the same CA; the result is an OPC UA connection that should be rejected.

The record

CVE
CVE-2026-6899
Published
Jun 9, 2026
Updated
Jun 9, 2026
Vendor
Systerel
Product
S2OPC
Classifications
CWE-299, T1190
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=1.5.0 <1.7.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Systerel · S2OPCversion=1.5.0 <1.7.3

Published CVSS scores

5.6GitLab CNACVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L

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

CWE-299Improper Check for Certificate Revocation
T1190Exploit Public-Facing Application

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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