CVE-2021-45934

Client crash via out-of-bounds packet write

Published Dec 31, 2021 · Updated Aug 4, 2024

Heap-based buffer overflow in wolfSSL wolfMQTT 1.9 allows context-dependent attackers to crash a client via a malformed MQTT packet. MqttClient_DecodePacket writes one byte beyond a heap allocation while decoding packet data reached through MqttClient_HandlePacket or MqttClient_WaitType. Exploitation requires a consuming application to deliver attacker-controlled packet data to the decoder, and published evidence establishes availability impact only.

CVSS severity5.5
Medium
EPSS probability0.89%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-based buffer overflow in wolfSSL wolfMQTT 1.9 allows context-dependent attackers to crash a client via a malformed MQTT packet. MqttClient_DecodePacket writes one byte beyond a heap allocation while decoding packet data reached through MqttClient_HandlePacket or MqttClient_WaitType. Exploitation requires a consuming application to deliver attacker-controlled packet data to the decoder, and published evidence establishes availability impact only.

The record

CVE
CVE-2021-45934
Published
Dec 31, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, T1499
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 31, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:N/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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