CVE-2021-37740Public exploitNetwork attack vector

Remote DoS via malformed SESSION_REQUEST

Published Apr 20, 2022 · Updated Aug 4, 2024

Denial of service in MDT SCN-IP100.03 and SCN-IP000.03 firmware before 3.0.4 allows remote attackers to interrupt KNXnet/IP Secure service. The KNXnet/IP Secure handler accepts a SESSION_REQUEST frame with a modified total-length field and leaves the device unresponsive to further requests. The attack requires network access to the KNXnet/IP Secure interface and recovery requires rebooting the affected device.

CVSS severity7.5
High
EPSS probability4.58%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in MDT SCN-IP100.03 and SCN-IP000.03 firmware before 3.0.4 allows remote attackers to interrupt KNXnet/IP Secure service. The KNXnet/IP Secure handler accepts a SESSION_REQUEST frame with a modified total-length field and leaves the device unresponsive to further requests. The attack requires network access to the KNXnet/IP Secure interface and recovery requires rebooting the affected device.

The record

CVE
CVE-2021-37740
Published
Apr 20, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 20, 2022CVE 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 vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.8NVDAV:N/AC:L/Au:N/C:N/I:N/A:C
7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

T1499Endpoint Denial of Service

Public exploit references

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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