Security Resilience

CVE-2026-84393

Published
08 September 2026
Modified
15 October 2026
CVSS Score v3.1 8.1
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.0025 15th percentile
Risk Priority 58 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2026-84393 is a high-severity Improper Validation of Certificate with Host Mismatch (CWE-297) vulnerability in Siemens (inferred from references). Its CVSS base score is 8.1 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Junk Data (T1001.001); ranked at the 15th 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 SC-23 (Session Authenticity) and SC-8 (Transmission Confidentiality and Integrity) — 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

A improper validation of certificate with host mismatch vulnerability in Fortinet FortiOS 7.6.1 through 7.6.6, FortiProxy 7.6.2 through 7.6.6 may allow attacker to information disclosure via <insert attack vector here>

CWE(s)
CWE-297

Related Threats

MITRE ATT&CK Enterprise Techniques

T1001.001 Junk Data Command And Control
Adversaries may add junk data to protocols used for command and control to make detection more difficult.
attack.mitre.org →
T1003.002 Security Account Manager Credential Access
Adversaries may attempt to extract credential material from the Security Account Manager (SAM) database either through in-memory techniques or through the Windows Registry where the SAM database is stored.
attack.mitre.org →
T1003.005 Cached Domain Credentials Credential Access
Adversaries may attempt to access cached domain credentials used to allow authentication to occur in the event a domain controller is unavailable.
attack.mitre.org →
T1003.008 /etc/passwd and /etc/shadow Credential Access
Adversaries may attempt to dump the contents of <code>/etc/passwd</code> and <code>/etc/shadow</code> to enable offline password cracking.
attack.mitre.org →
T1006 Direct Volume Access Stealth
Adversaries may directly access a volume to bypass file access controls and file system monitoring.
attack.mitre.org →
T1007 System Service Discovery Discovery
Adversaries may try to gather information about registered local system services.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2025-46408Shared CWE-297
CVE-2026-54275Shared CWE-297
CVE-2026-19553Shared CWE-297
CVE-2025-3501Shared CWE-297
CVE-2025-59060Shared CWE-297
CVE-2024-2466Shared CWE-297
CVE-2025-42921Shared CWE-297
CVE-2026-15925Shared CWE-297
CVE-2026-35563Shared CWE-297
CVE-2026-48145Shared CWE-297

Affected Assets

Siemens
—
inferred from references and description; NVD did not file a CPE for this CVE

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V17.2.8

Mitigating Controls (NIST 800-53 r5) AI

SC-23 Session Authenticity good match

Protecting session authenticity structurally requires proper certificate validation to bind the presented certificate to the intended host.

SC-8 Transmission Confidentiality and Integrity good match

Requiring confidentiality and integrity of transmitted data necessitates correct TLS certificate validation with host-name checking.

SA-8 Security and Privacy Engineering Principles partial match

Security engineering principles require correct implementation of certificate validation (including hostname matching) when cryptography is used.

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 partial match
blocks

Server/service authentication via certificates directly requires correct host validation.

PR.DS-02 partial match
blocks

Protecting data-in-transit integrity depends on proper certificate validation to prevent MITM.

PR.PS-06 partial match
blocks

Secure development practices include coding correct certificate validation logic.

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.7.2 Physical entry partial match
removes
A.8.19 Installation of software on operational systems partial match
removes
A.8.20 Networks security partial match
degrades

Network security controls include certificate validation and host-name verification to prevent man-in-the-middle attacks.

A.8.21 Security of network services partial match
degrades

Security of network services requires proper TLS configuration and certificate validation for service endpoints.

A.8.24 Use of cryptography partial match
blocks

A.8.24 mandates proper use of cryptography (algorithms, key management, certificates for protection) but does not address or stop exploitation of a certificate-hostname validation flaw in the product's TLS handshake logic

A.8.26 Application security requirements partial match
blocks

Application security requirements include secure communication and certificate validation for external services.

References