Cyber Resilience

CVE-2021-27391

Critical

Published: 14 September 2021

Published
14 September 2021
Modified
23 April 2025
KEV Added
Patch
CVSS Score v3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.0286 86.6th percentile
Risk Priority 21 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2021-27391 is a critical-severity Classic Buffer Overflow (CWE-120) vulnerability in Siemens Apogee Mbc \(Ppc\) \(P2 Ethernet\) Firmware. Its CVSS base score is 9.8 (Critical).

Operationally, ranked in the top 13.4% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

EU & UK References

Vulnerability details

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 >=…

more

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.

CWE(s)

Related Threats

No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.

Affected Assets

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

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

addresses: CWE-120

Platform-independent managed code eliminates the need for unchecked native buffer copies that are the root cause of classic buffer overflows.

References