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CVE Record

CVE-2021-45938: wolfSSL wolfMQTT 1.9 has a heap-based buffer overflow in MqttClient_DecodePacket (called from MqttClient_Wa...

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

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

wolfMQTT 1.9 has a heap buffer overflow in packet decoding. For executives, the business concern is unmanaged embedded or IoT software that includes this library. The public bundle does not provide CVSS, affected deployment conditions, or confirmed impact, so urgency depends on whether your products process MQTT traffic with wolfMQTT 1.9.

Executive priority

Prioritize if wolfMQTT 1.9 is used in internet-facing, customer-facing, or safety-sensitive embedded systems. If no wolfMQTT 1.9 usage exists, business urgency is low. Because severity and impact are not scored in the bundle, decide priority from exposure and vendor remediation evidence.

Technical view

CVE-2021-45938 is a heap-based buffer overflow in wolfSSL wolfMQTT 1.9, specifically MqttClient_DecodePacket, reached from MqttClient_WaitType and MqttClient_Unsubscribe. The provided sources identify the vulnerable code path and OSS-Fuzz lineage, but do not state exploitability, authentication requirements, or a fixed release version.

Likely exposure

Exposure is most likely in applications, firmware, or services that bundle wolfSSL wolfMQTT 1.9 and parse MQTT packets. The bundle does not identify specific downstream products, operating systems, cloud services, or distributions.

Exploitation context

The source bundle does not show CISA KEV listing or any cited evidence of active exploitation. It also does not provide public exploit status. Treat this as a memory-corruption defect requiring inventory-driven validation, not as confirmed exploited activity.

Researcher notes

The key facts are narrow: affected version 1.9, heap overflow, MqttClient_DecodePacket, and call paths through wait and unsubscribe handling. Missing evidence includes CVSS, CWE assignment, exploit status, affected configurations, and fixed version. Avoid expanding impact claims without vendor or test evidence.

Mitigation direction

  • Inventory software and firmware that includes wolfMQTT.
  • Identify any use of wolfMQTT version 1.9.
  • Check wolfSSL guidance and the referenced commit for corrected code.
  • Upgrade or rebuild affected components when vendor guidance confirms the fix.
  • Limit exposure of MQTT-processing components where operationally feasible.

Validation and detection

  • Review SBOMs, lockfiles, and build manifests for wolfMQTT.
  • Confirm deployed binaries or firmware are not using wolfMQTT 1.9.
  • Map MQTT packet processing paths to wolfMQTT usage.
  • Verify remediation against vendor-referenced fixed code or release notes.
  • Record unsupported or unverified embedded dependencies for follow-up.
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-2021-45938 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.