CVE-2021-31887Network attack vector

Authenticated code execution via oversized FTP commands

Published Nov 9, 2021 · Updated Aug 3, 2024

Stack-based buffer overflow in Siemens Nucleus NET FTP server allows remote authenticated users to execute code or crash devices. The PWD and XPWD command handler fails to validate command length before copying input into a stack buffer. A reachable, enabled FTP service and valid FTP access are required; Desigo products disable FTP by default, and successful exploitation can compromise or interrupt the embedded device.

CVSS severity8.8
High
EPSS probability2.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack-based buffer overflow in Siemens Nucleus NET FTP server allows remote authenticated users to execute code or crash devices. The PWD and XPWD command handler fails to validate command length before copying input into a stack buffer. A reachable, enabled FTP service and valid FTP access are required; Desigo products disable FTP by default, and successful exploitation can compromise or interrupt the embedded device.

The record

CVE
CVE-2021-31887
Published
Nov 9, 2021
Updated
Aug 3, 2024
Vendor
Siemens
Product
TALON TC Compact (BACnet)
Classifications
CWE-787, CWE-170, T1210
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Nov 9, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=All versions < V3.5.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Siemens · TALON TC Compact (BACnet)version=All versions < V3.5.4
Siemens · APOGEE PXC Modular (P2 Ethernet)version=All versions < V2.8.19
Siemens · Desigo PXC00-Uversion=All versions >= V2.3 and < V6.30.016
Siemens · Desigo PXC100-E.Dversion=All versions >= V2.3 and < V6.30.016
Siemens · APOGEE MBC (PPC) (BACnet)version=All versions
Siemens · Desigo PXC22-E.Dversion=All versions >= V2.3 and < V6.30.016
Siemens · APOGEE MEC (PPC) (BACnet)version=All versions
Siemens · Desigo PXM20-Eversion=All versions >= V2.3 and < V6.30.016
Siemens · Nucleus Source Codeversion=All versions
Siemens · Desigo PXC22.1-E.Dversion=All versions >= V2.3 and < V6.30.016
Siemens · Nucleus NET for Nucleus PLUSversion=All versions
Siemens · APOGEE MEC (PPC) (P2 Ethernet)version=All versions
Siemens · Nucleus ReadyStart V3version=All versions < V2017.02.4
Siemens · APOGEE PXC Compact (BACnet)version=All versions < V3.5.4
Siemens · TALON TC Modular (BACnet)version=All versions < V3.5.4
Siemens · Desigo PXC64-Uversion=All versions >= V2.3 and < V6.30.016
Siemens · APOGEE MBC (PPC) (P2 Ethernet)version=All versions
Siemens · Desigo PXC50-E.Dversion=All versions >= V2.3 and < V6.30.016
Siemens · Desigo PXC12-E.Dversion=All versions >= V2.3 and < V6.30.016
Siemens · Desigo PXC36.1-E.Dversion=All versions >= V2.3 and < V6.30.016
Siemens · APOGEE PXC Modular (BACnet)version=All versions < V3.5.4
Siemens · APOGEE PXC Compact (P2 Ethernet)version=All versions < V2.8.19
Siemens · Desigo PXC00-E.Dversion=All versions >= V2.3 and < V6.30.016
Siemens · Desigo PXC001-E.Dversion=All versions >= V2.3 and < V6.30.016
Siemens · Desigo PXC128-Uversion=All versions >= V2.3 and < V6.30.016
Siemens · Desigo PXC200-E.Dversion=All versions >= V2.3 and < V6.30.016

Published CVSS scores

6.5NIST NVDAV:N/AC:L/Au:S/C:P/I:P/A:P
8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
CWE-170Improper Null Termination
T1210Exploitation of Remote Services

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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