PatchTheCVECVE-2021-37740: A denial of service vulnerability exists in MDT's firmware for the KNXnet/IP Secure router SCN-IP100.03 and KN
CVE-2021-37740 is a high-severity flaw (CVSS 7.5) affecting scn-ip000.03 firmware, scn-ip100.03 firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
A denial of service vulnerability exists in MDT's firmware for the KNXnet/IP Secure router SCN-IP100.03 and KNX IP interface SCN-IP000.03 before v3.0.4, that allows a remote attacker to turn the device unresponsive to all requests on the KNXnet/IP Secure layer, until the device is rebooted, via a SESSION_REQUEST frame with a modified total length field.
Why this priority
- High severity
- EPSS top 8%: very likely to be exploited
- Public exploit reference
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 7.5 (High) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 4.6% (top 8%) |
| CISA exploited list | No |
| Published | 2022-04-20 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2021-37740?
scn-ip000.03 firmware: upgrade to 3.0.4; scn-ip100.03 firmware: upgrade to 3.0.4. Exact commands for each OS are on this page.
Is CVE-2021-37740 being exploited?
CVE-2021-37740 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2021-37740 affect?
CVE-2021-37740 affects scn-ip000.03 firmware, scn-ip100.03 firmware. Severity is high (CVSS 7.5). A denial of service vulnerability exists in MDT's firmware for the KNXnet/IP Secure router SCN-IP100.03 and KNX IP interface SCN-IP000.03 before v3.0.4, that allows a remote attacker to turn the device unresponsive to all requests on the KN
How urgent is CVE-2021-37740?
Priority 59/100. High severity; EPSS top 8%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action