BSI C5:2020 PSS-03 — Online Register of Known Vulnerabilities

What this control requires

Maintains a daily-updated online vulnerability register per CVSS, accessible to customers. Details updates and deployment responsibilities, enabling risk assessments and timely mitigations to protect cloud customer data and services

In plain English

Maintains a daily-updated online vulnerability register per CVSS, accessible to customers. In practice, this means you can prove you risk cloud customer data-level controls on a defined cadence.

Why it matters

BSI C5 is the default cloud-security baseline German public-sector buyers and many DAX-listed enterprises expect; gaps here directly block procurement in the DACH region and frequently appear as must-have items in EU public-tender documents.

This control is rated high. Auditors expect a named owner, a remediation SLA, and a tooling artefact that evidences continuous operation.

What an auditor looks for

A C5 attesting auditor (under ISAE 3000 / IDW PS 860) tests both the design and — for a Type 2 — the operating effectiveness over the attestation period. For each criterion they look for both the Basic and any in-scope Additional objectives.

Within Platform & Service Security, the assessor will trace your implementation back to the catalogue reference (Criterion PSS-03) and look for objective evidence on the latest two assessment cycles.

How to implement

Vulnerability Management

Scanners. Pair an unauthenticated scanner (Nessus / Qualys / Tenable.io) for external surface with an authenticated agent for OS/library CVEs on every host.

SLA. Document remediation SLAs by CVSS / EPSS: critical 7 days, high 30 days, medium 90 days; report monthly trend to leadership.

Containers. Scan images in CI (Trivy / Grype / Snyk Container) AND at runtime; block deploys on critical findings without exception.

Operational checklist

• Risk. Document the trigger, the owner and the cadence.
• Review. Document the trigger, the owner and the cadence.
• Security. Document the trigger, the owner and the cadence.
• Data. Document the trigger, the owner and the cadence.
• Access. Document the trigger, the owner and the cadence.
• Scope: cloud customer data, management.

Evidence to collect

• Identity Scan. IAM / IdP exports — Entra ID, Okta, IAM Identity Center, Workspace directory — showing accounts, roles, MFA state and last sign-in.

Identity analytics (Okta, SailPoint, Access Analyzer) demonstrates least-privilege. Focus: Online Register of Known Vulnerabilities.

Common pitfalls

• Scans that hit only the perimeter; missing authenticated scans of OS, runtime libs and base images so most CVEs are invisible.

How it maps to other frameworks

Computed from shared tags, control component and key-operation subjects — handy when you are reconciling controls across an audit.

• ISO/IEC 27001:2022 A.8.23 — Web filtering
• SOC 2 (2017 TSC) CC1.5 — Accountability for Internal Control Responsibilities
• NIST SP 800-171 Rev. 3 3.13.4 — Information in Shared System Resources
• CIS Controls v8 9.2 — Use DNS Filtering Services
• ISO/IEC 27701:2025 A.3.8 — Identity management

Related controls in BSI C5:2020

• Criterion PSS-09 — Authorisation Mechanisms
• Criterion AM-05 — Commitment to Permissible Use, Safe Handling and Return of Assets
• Criterion HR-01 — Verification of qualification and trustworthiness
• Criterion HR-05 — Responsibilities in the event of termination or change of employment
• Criterion IDM-03 — Locking and withdrawal of user accounts in the event of inactivity or multiple failed logins
• Criterion INQ-03 — Conditions for Access to or Disclosure of Data in Investigation Requests

References

• Bundesamt für Sicherheit in der Informationstechnik (BSI) — BSI C5:2020
• Catalogue identifier: Criterion PSS-03

Topics: identity accessidentity managementaccess reviewprivileged accessvulnerability management