CVE intelligence and bounded remediation

CVE-2021-34434 — Eclipse Mosquitto security vulnerability

Medium CVSS 5.3

In Eclipse Mosquitto versions 2.0 to 2.0.11, when using the dynamic security plugin, if the ability for a client to make subscriptions on a topic is revoked when a durable client is offline, then existing subscriptions for that client are not revoked.

Severity
Medium
CVSS
5.3 (3.1)
Published
2021-08-30
CISA KEV
Not currently listed
Ecosystem
software/application
Weaknesses
CWE-285, CWE-863

Affected products

  • eclipse / mosquitto
  • fedoraproject / fedora / 34
  • fedoraproject / fedora / 35

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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