CVE intelligence and bounded remediation

CVE-2021-33175 — Emqx Emq X Broker security vulnerability

High CVSS 7.5

EMQ X Broker versions prior to 4.2.8 are vulnerable to a denial of service attack as a result of excessive memory consumption due to the handling of untrusted inputs. These inputs cause the message broker to consume large amounts of memory, resulting in the application being terminated by the operating system.

Severity
High
CVSS
7.5 (3.1)
Published
2021-06-08
CISA KEV
Not currently listed
Ecosystem
software/application
Weaknesses
CWE-502, CWE-770

Affected products

  • emqx / emq_x_broker

Matched remediation archetype

Unsafe deserialization and object reconstruction

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Check exposure

  • Inventory serialization formats accepted from requests, queues, caches, files, cookies, and cross-service messages.
  • Trace whether untrusted input can select classes, types, callbacks, constructors, or object hooks during decoding.
  • Identify signing, schema validation, trust-boundary, and compatibility settings for each decoder.

Remediate safely

  • Replace native object deserialization with a data-only format and explicit schema validation.
  • If replacement is not immediate, use a safe decoder with a minimal type allowlist and disable polymorphic or executable hooks.
  • Update the affected library and add inert tests for unknown types, extra fields, malformed nesting, and unsigned data.

Authoritative sources

Complete CVE record and remediation plan

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