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CVE Record

CVE-2021-45933: wolfSSL wolfMQTT 1.9 has a heap-based buffer overflow (8 bytes) in MqttDecode_Publish (called from MqttClie...

wolfSSL wolfMQTT 1.9 has a heap-based buffer overflow (8 bytes) in MqttDecode_Publish (called from MqttClient_DecodePacket and MqttClient_HandlePacket).

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2021-45933 is a heap buffer overflow in wolfSSL wolfMQTT 1.9. The public bundle identifies an 8-byte overflow during MQTT PUBLISH packet decoding. Business risk depends on whether the library is present in products that process MQTT traffic, especially embedded or IoT systems.

Executive priority

Treat this as an inventory and supplier-risk item unless wolfMQTT 1.9 is confirmed in exposed MQTT-processing systems. Prioritize embedded, IoT, and operational environments where library updates require firmware or vendor coordination.

Technical view

The issue is reported in MqttDecode_Publish, reachable through MqttClient_DecodePacket and MqttClient_HandlePacket in wolfMQTT 1.9. The bundle references an upstream wolfMQTT commit and OSS-Fuzz records, but provides no CVSS score, CWE, CPEs, downstream product list, or detailed impact statement.

Likely exposure

Exposure is likely limited to software or firmware that embeds wolfSSL wolfMQTT 1.9 and processes MQTT PUBLISH messages. The source bundle does not identify affected CPEs, appliances, vendors, cloud services, or default-exposed deployments.

Exploitation context

The bundle does not show CISA KEV listing or any cited evidence of active exploitation. OSS-Fuzz involvement suggests the bug was found through automated fuzz testing, but the available evidence does not establish real-world exploitation or weaponized public use.

Researcher notes

The evidence supports a narrow technical claim: an 8-byte heap overflow in wolfMQTT 1.9 PUBLISH decoding. Missing CVSS, CWE, CPEs, and impact details reduce confidence in severity. Do not assume affected downstream products without SBOM or vendor confirmation.

Mitigation direction

  • Inventory applications, firmware, and vendors that use wolfMQTT 1.9.
  • Review wolfSSL guidance and the referenced upstream commit for the fixed code path.
  • Upgrade or rebuild affected components when a vendor-supported fixed release is available.
  • Restrict MQTT traffic to trusted brokers and clients where wolfMQTT exposure remains unresolved.
  • Request SBOM or library-version confirmation from device and software suppliers.

Validation and detection

  • Check SBOMs and build manifests for wolfMQTT 1.9.
  • Ask vendors whether their products include wolfMQTT and whether this CVE is fixed.
  • Confirm deployed binaries or firmware were rebuilt after the referenced fix.
  • Review MQTT-facing components that parse PUBLISH packets from untrusted sources.
  • Track remediation status separately for embedded devices with delayed firmware updates.
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-2021-45933 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.