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CVE Record

CVE-2021-45934: wolfSSL wolfMQTT 1.9 has a heap-based buffer overflow in MqttClient_DecodePacket (called from MqttClient_Ha...

wolfSSL wolfMQTT 1.9 has a heap-based buffer overflow in MqttClient_DecodePacket (called from MqttClient_HandlePacket and MqttClient_WaitType).

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2021-45934 is a heap-based buffer overflow reported in wolfSSL wolfMQTT 1.9. It affects packet decoding in the MQTT client library. The business risk depends on where wolfMQTT is embedded and whether untrusted MQTT traffic reaches it. The provided sources do not include CVSS, active exploitation, or a named fixed release.

Executive priority

Treat this as a targeted dependency investigation rather than a confirmed emergency. Prioritize environments using MQTT in embedded, IoT, or operational systems, especially where wolfMQTT 1.9 is reachable from untrusted networks.

Technical view

The issue is in MqttClient_DecodePacket, called from MqttClient_HandlePacket and MqttClient_WaitType. The source bundle links it to OSS-Fuzz and a wolfMQTT commit, indicating a memory-safety flaw found during fuzzing. No exploitability details, CWE assignment, affected CPEs, or fixed version are provided in the bundle.

Likely exposure

Exposure is most likely in products, firmware, or services that embed wolfSSL wolfMQTT 1.9 and decode MQTT packets. Static linking may hide the vulnerable component in appliances or IoT software. The provided affected-product metadata is incomplete.

Exploitation context

There is no KEV listing and no cited source in the bundle states active exploitation. The available evidence points to an OSS-Fuzz-discovered crash or memory-safety issue, but does not describe real-world exploitation, prerequisites, or impact beyond heap overflow.

Researcher notes

The bundle lacks CVSS, CWE, CPEs, fixed release data, and exploitation evidence. Analysis should focus on component provenance, static linkage, reachable MQTT decode paths, and confirming whether the referenced upstream commit is present in local builds.

Mitigation direction

  • Inventory software and firmware for wolfMQTT 1.9 usage.
  • Check wolfSSL guidance and release notes for the fix containing commit 84d4b53122e0fa0280c7872350b89d5777dabbb2.
  • Upgrade or rebuild embedded components with a corrected wolfMQTT version when confirmed.
  • Restrict untrusted MQTT traffic to affected clients until remediation is complete.
  • Monitor vendor advisories for fixed-version and impact clarification.

Validation and detection

  • Review SBOMs, dependency manifests, and firmware component lists for wolfMQTT 1.9.
  • Confirm whether MQTT client code paths call packet decoding on untrusted broker or network input.
  • Verify deployed builds include the wolfMQTT correction referenced by the linked commit.
  • Check crash telemetry for MQTT decoding faults in wolfMQTT-based components.
  • Document any static-linking cases where package scanners may miss wolfMQTT.
Prepared
Confidence
medium
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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CVE-2021-45934 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
4Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.