Cyber Resilience

CVE-2026-6899

Published
09 June 2026
Modified
17 June 2026
CVSS Score v3.1 5.6
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
EPSS Score 0.0011 1th percentile
Risk Priority 35 floored blend · peak EPSS

Summary

CVE-2026-6899 is a medium-severity Improper Check for Certificate Revocation (CWE-299) vulnerability. Its CVSS base score is 5.6 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Subvert Trust Controls (T1553); ranked at the 1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to IA-5 (Authenticator Management) and SC-13 (Cryptographic Protection) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

A07:2025 Authentication Failures

EU & UK References

Vulnerability Data

Check for certificate revocation only considers the first matching CRL and ignores other valid CRLs of the same CA in the CycloneCrypto cryptographic wrapper of S2OPC library. It might allow connection between an OPC UA client and server using a…

more

revoked certificate.

CWE(s)
CWE-299

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1553 Subvert Trust Controls Defense Impairment
Adversaries may undermine security controls that will either warn users of untrusted activity or prevent execution of untrusted programs.
attack.mitre.org →
Why these techniques?

Improper revocation check (CWE-299) directly enables use of revoked certificates, subverting trust controls on authentication certs.

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

Likely ATT&CK TechniquesAI

Techniques this vulnerability likely enables, inferred from its description, weakness type, and attributed-actor tradecraft. Confidence is per-technique.

T1133 External Remote Services Persistenceconfidence: HIGH
Bypassing CRL checks directly allows an attacker to authenticate to an OPC UA server using a revoked certificate, enabling access via external remote services.
attack.mitre.org →
inferred from description + CWE · MITRE ATT&CK Enterprise v19.0

CVEs Like This One

CVE-2026-56821Shared CWE-299
CVE-2025-36057Shared CWE-299
CVE-2025-3085Shared CWE-299
CVE-2026-4428Shared CWE-299
CVE-2025-11955Shared CWE-299
CVE-2026-9636Shared CWE-299
CVE-2024-56138Shared CWE-299
CVE-2023-23690Shared CWE-299

Affected Assets

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)
  • SC-13 Cryptographic Protection
  • IA-5 Authenticator Management
  • AC-17 Remote Access
Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V12.1.4

Mitigating Controls (NIST 800-53 r5) AI

SC-13 Cryptographic Protection good match
prevent

Directly requires correct cryptographic protection including proper certificate validation and revocation checking for all PKI operations.

IA-5 Authenticator Management good match
prevent

Mandates management of authenticators and PKI certificates, explicitly requiring revocation status verification before acceptance.

AC-17 Remote Access partial match
prevent

Enforces secure remote access authentication, which for OPC UA relies on valid non-revoked certificates to prevent unauthorized connections.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.AA-03 mostly match
prevents

Certificate-based authentication requires valid, non-revoked certificates; proper revocation checking is a core implementation detail of this control.

PR.DS-02 mostly match
prevents

Protecting data-in-transit commonly relies on TLS certificate validation that includes revocation status checks.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.24 Use of cryptography mostly match
prevents

Mandates use of cryptography including certificate validation and revocation checking.

A.8.29 Security testing in development and acceptance mostly match
detects

Security testing can detect missing or incorrect certificate revocation checks.

A.8.28 Secure coding partial match
prevents

Secure coding practices should include proper certificate revocation verification.

A.8.5 Secure authentication partial match
prevents

Requires secure authentication mechanisms that rely on valid certificates.

A.8.20 Networks security none match
none

Network security controls can enforce certificate validation at network boundaries.

A.8.21 Security of network services none match
none

Security of network services includes certificate-based authentication and revocation checks.

References