CVE intelligence and bounded remediation

CVE-2021-3987 — An improper access control vulnerability exists in janeczku/calibre-web

Medium CVSS 5.4

An improper access control vulnerability exists in janeczku/calibre-web. The affected version allows users without public shelf permissions to create public shelves. The vulnerability is due to the `create_shelf` method in `shelf.py` not verifying if the user has the necessary permissions to create a public shelf. This issue can lead to unauthorized actions being performed by users.

Severity
Medium
CVSS
5.4 (3.0)
Published
2024-11-15
CISA KEV
Not currently listed
Ecosystem
software/application
Weaknesses
CWE-284, CWE-862

Affected products

  • janeczku / calibre-web

Matched remediation archetype

Authorization bypass, IDOR, and cross-tenant access

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Check exposure

  • Map object and action authorization checks across API, UI, batch, import/export, and background-job paths.
  • Identify tenant, ownership, role, and policy boundaries for affected resources and administrative operations.
  • Use synthetic fixtures to compare intended access matrices without accessing another user's real data.

Remediate safely

  • Enforce server-side authorization at each resource access and state transition using the authenticated principal and trusted tenant context.
  • Scope data queries by tenant and ownership; treat client-supplied identifiers, roles, and policy claims as untrusted.
  • Add deny-by-default policy tests for horizontal and vertical access across every affected transport.

Authoritative sources

Complete CVE record and remediation plan

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