CVE-2021-27391

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure, data tampering, service disruption.

Exploit odds

3.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-09-14 11:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:44 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 3.4% in the next 30 days (EPSS).
• Severity: 9.8 CRITICAL (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-09-14 11:15 UTC

Last modified

2026-06-17 03:44 UTC

Exploit probability

3.4% · EPSS, next 30 days

Weakness

CWE-120 · Classic buffer overflow

Record status

Modified

Affected

• Siemens Apogee Mbc \(ppc\) \(p2 ethernet\) Firmware ≤ 2.6.3
• Siemens Apogee Mec \(ppc\) \(p2 ethernet\) Firmware ≤ 2.6.3
• Siemens Apogee Pxc Bacnet Automation Controller Firmware < 3.5.3
• Siemens Apogee Pxc Compact \(p2 ethernet\) Firmware ≤ 2.8
• Siemens Apogee Pxc Modular \(bacnet\) Firmware < 3.5.3
• Siemens Apogee Pxc Modular \(p2 ethernet\) Firmware ≤ 2.8
• Siemens Talon Tc Compact \(bacnet\) Firmware < 3.5.3
• Siemens Talon Tc Modular \(bacnet\) Firmware < 3.5.3

Attack profile CVSS 3.1 · 9.8

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-27391.md and follow it. Check whether this project is affected by CVE-2021-27391. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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