CVE-2021-31886
No exploitation reported by the sources we read.
- Published2021-11-09
- Fixed in3.5.4 · 2.8.19
- WeaknessCWE-170 · CWE-787
Am I affected?
Debian, Ubuntu or Red Hat sometimes backport a fix without changing the upstream version number: such a version reads « to verify », never « affected ».With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.
Description
A vulnerability has been identified in APOGEE MBC (PPC) (BACnet) (All versions), APOGEE MBC (PPC) (P2 Ethernet) (All versions), APOGEE MEC (PPC) (BACnet) (All versions), APOGEE MEC (PPC) (P2 Ethernet) (All versions), APOGEE PXC Compact (BACnet) (All versions < V3.5.4), APOGEE PXC Compact (P2 Ethernet) (All versions < V2.8.19), APOGEE PXC Modular (BACnet) (All versions < V3.5.4), APOGEE PXC Modular (P2 Ethernet) (All versions < V2.8.19), Desigo PXC00-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC00-U (All versions >= V2.3 and < V6.30.016), Desigo PXC001-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC100-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC12-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC128-U (All versions >= V2.3 and < V6.30.016), Desigo PXC200-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC22-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC22.1-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC36.1-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC50-E.D (All versions >= V2.3 and < V6.30.016), Desigo PXC64-U (All versions >= V2.3 and < V6.30.016), Desigo PXM20-E (All versions >= V2.3 and < V6.30.016), Nucleus NET (All versions), Nucleus ReadyStart V3 (All versions < V2017.02.4), Nucleus Source Code (All versions), TALON TC Compact (BACnet) (All versions < V3.5.4), TALON TC Modular (BACnet) (All versions < V3.5.4). FTP server does not properly validate the length of the “USER” command, leading to stack-based buffer overflows. This may result in Denial-of-Service conditions and Remote Code Execution. (FSMD-2021-0010)
Timeline
dates in UTC- 2021-11-0912:15CVE publishedNVD
Observed activity
isMalicious corpus · updated 2026-10-23 18:48 UTCBlock these indicators
- Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-31886?format=txt
- CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-31886?format=csv
- TAXII collection of exploited CVEs
- The EDL and CSV take an API key on the Pro plan.
Versions per branch
NVD| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 3.5 | < 3.5.4 | 3.5.4 | NVD |
| 2.8 | < 2.8.19 | 2.8.19 | NVD |
| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 3.5 | < 3.5.4 | 3.5.4 | NVD |
| 2.8 | < 2.8.19 | 2.8.19 | NVD |
| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| — | all versions | no fix published | NVD |
19 more products in the sources.
as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.
Distribution builds and vendor advisories
Packages from OSV.dev and products from the vendors' CSAF advisories.
version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.
Vendor advisories
Siemens Nucleus RTOS TCP/IP Stack
Nucleus NET · Nucleus ReadyStart V3 · Nucleus Source Code
Siemens Nucleus RTOS-based APOGEE and TALON Products (Update C)
APOGEE MBC (PPC) (BACnet) · APOGEE MBC (PPC) (P2 Ethernet) · APOGEE MEC (PPC) (BACnet) · +20 more
Fix
- Update Siemens apogee pxc compact firmware to 3.5.4 · 2.8.19
- Vendor fix CISA ICSA-21-315-07 · 4 productsUpdate to V3.5.4 or later version
- Vendor fix CISA ICSA-21-315-07 · 2 productsUpdate to V2.8.19 or later version
- Vendor fix CISA ICSA-21-315-07 · 13 productsUpdate to V6.30.016 or later version
- Vendor fix CISA ICSA-21-313-03 · 1 productUpdate to V2017.02.4 or later version
- Vendor fix CISA ICSA-21-313-03 · 1 productContact customer support to receive patch and update information
- Mitigation from the vendor CISA ICSA-21-315-07 · 23 productsCVE-2021-31881, CVE-2021-31882, CVE-2021-31883, CVE-2021-31884: Disable the DHCP client and use static IP address configuration instead (Note that the DHCP client is disabled by default on APOGEE/TALON and Desigo products.)
Advisories and patches
- cert-portal.siemens.comVendor Advisory
- cert-portal.siemens.comVendor Advisory
Detection
- Nuclei template
- none so far ProjectDiscovery
- Exploit-DB
- no entry Exploit-DB
- Proof-of-concept repositories
- none listed PoC-in-GitHub
Sources
- NVDCVSS 3.19.8read 2026-10-23
- NVDCVSS 2.07.5read 2026-10-23
- CNAweakness (CWE)CWE-170read 2026-10-23
- NVDweakness (CWE)CWE-787read 2026-10-23
- FIRST EPSSEPSS score3.0 %2026-10-22
Technical details
- CVSS v3 Vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Published
- 2021-11-09
- Last Modified
- 2026-06-17
- NVD status
- Modified
Frequently asked questions
What is CVE-2021-31886?
Is CVE-2021-31886 actively exploited?
What is the CVSS score for CVE-2021-31886?
Running APOGEE MBC (PPC) (BACnet) (All? Hear about its next vulnerability
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Related vulnerabilities
Same product first, then the same vendor advisory and the same publication week.