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Improper Signature VerificationWeakness · CWE-347

CVE-2026-56451

CRITICAL · 10.0 CVSS v3.1 Published 2026-07-14
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click 5 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A vulnerability has been identified in Opcenter X (All versions < V2604). Affected applications do not properly validate the algorithm specified in the JSON Web Token (JWT) header. This could allow an unauthenticated remote attacker to forge arbitrary JWT, bypass authentication mechanisms and impersonate any user including administrative accounts, potentially gaining full unauthorized access to the application.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Opcenter X versions before V2604 fail to properly validate the algorithm field in JWT token headers, allowing attackers to manipulate this field (e.g., using 'none' or algorithm confusion) to forge valid tokens. This enables complete authentication bypass and impersonation of any user including administrators.

MitigationUpgrade to Opcenter X V2604 or later which properly validates JWT algorithms. If immediate patching is not possible, implement server-side validation to explicitly reject 'none' algorithm and only accept expected, configured algorithms.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed Opcenter X version
    Check the product version through the system administration interface, installation directory, or version lookup command specific to the Opcenter X deployment
    Affected if The installed version is any release before V2604 (e.g., V2506, V2409, etc.)
  2. Confirm JWT-based authentication is in use
    Inspect the authentication configuration or logs to determine whether the system uses JWT tokens for user sessions
    Affected if JWT tokens are being used for authentication in the environment
  3. Test JWT algorithm validation behavior
    Craft a test JWT with 'alg:none' in the header and attempt to use it against the authentication endpoint, or inspect server-side code/configuration for explicit algorithm validation logic
    Affected if The system accepts JWTs with 'none' algorithm or lacks explicit algorithm validation that only allows expected algorithms (HS256, RS256, etc.)
  4. Review JWT library or framework in use
    Identify which JWT library or component handles token validation within Opcenter X, and check its configuration for algorithm restrictions
    Affected if The JWT library is configured to allow any algorithm or defaults to not strictly validating the alg header field

A user is affected if Opcenter X version is before V2604 AND the system uses JWT-based authentication, particularly if algorithm validation is not explicitly enforced in the JWT handling configuration.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to Opcenter X V2604 or later which properly validates JWT algorithms. If immediate patching is not possible, implement server-side validation to explicitly reject 'none' algorithm and only accept expected, configured algorithms.

Recommended fix Moderate confidence

Opcenter X V2604 or later

  1. 1. Identify the current installed version of Opcenter X by accessing the application's version information panel or checking system documentation.
  2. 2. Download Opcenter X version V2604 or later from the official Siemens support portal or certified distribution channel.
  3. 3. Before upgrading, perform a complete backup of the Opcenter X database, configuration files, and any custom integrations.
  4. 4. Review upgrade prerequisites and ensure the target system meets hardware, software, and compatibility requirements for V2604.
  5. 5. Execute the upgrade procedure following the official Siemens Opcenter X migration guide, ensuring minimal downtime.
  6. 6. After upgrade completion, verify that the JWT algorithm validation is now properly enforced by testing authentication flows.
  7. 7. Validate that existing user accounts and role mappings function correctly post-upgrade.
  8. 8. Monitor system logs for any authentication anomalies in the days following the upgrade.
Caveat Check Siemens release notes for V2604 for any configuration or integration changes that may require adjustment

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing8.0 h
  • Review / QA4.0 h
24.0 hours of engineering $4,160
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-56451 in production — separate from our analysis above.

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