Is CVE-2021-27391 actively exploited?

No active exploitation of CVE-2021-27391 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2021-27391 be exploited remotely?

Yes. CVE-2021-27391 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2021-27391?

CVE-2021-27391 has a CVSS score of 9.8 (CRITICAL).

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CRITICAL

CVE-2021-27391

CWE-120Published: September 14, 2021· Updated: Jun 17, 2026

9.8

CVSS v3.1

Official 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.

NVD Source

Technical Analysis

CVE-2021-27391 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.8.

CVSS v3.1 Vector Breakdown

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges Req.None

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected Vendors & Products

siemens16 product(s)

apogee mbc \(ppc\) \(p2 ethernet\) firmwareapogee mbc \(ppc\) \(p2 ethernet\)apogee mec \(ppc\) \(p2 ethernet\) firmwareapogee mec \(ppc\) \(p2 ethernet\)apogee pxc bacnet automation controller firmwareapogee pxc bacnet automation controllerapogee pxc compact \(p2 ethernet\) firmwareapogee pxc compact \(p2 ethernet\)apogee pxc modular \(bacnet\) firmwareapogee pxc modular \(bacnet\)apogee pxc modular \(p2 ethernet\) firmwareapogee pxc modular \(p2 ethernet\)+4

Source: NVD CPE · 16 total CPE entries