Is CVE-2021-27391 in the CISA KEV catalog?

No. CVE-2021-27391 is not currently on the CISA Known Exploited Vulnerabilities list.

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

CVE-2021-27391 has a CVSS v3 base score of 9.8 (CRITICAL).

What is the EPSS score for CVE-2021-27391?

CVE-2021-27391 has an EPSS score of 3.26% (87th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-27391?

Upgrade apogee pxc bacnet automation controller firmware to 3.5.3 or later. Fixes are available for 4 affected products.

CVE & CISA-KEV Catalog

CVE-2021-27391

CRITICALEPSS 87th pctl

9.8

CVSS v3

NVD

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.

CWE-120Classic Buffer Overflow

How to fix

Remediation Available

apogee pxc bacnet automation controller firmwareNVD

Affected:< 3.5.3Fixed in:3.5.3CVE-2021-27391derived from NVD

apogee pxc modular \(bacnet\) firmwareNVD

Affected:< 3.5.3Fixed in:3.5.3CVE-2021-27391derived from NVD

talon tc compact \(bacnet\) firmwareNVD

Affected:< 3.5.3Fixed in:3.5.3CVE-2021-27391derived from NVD

talon tc modular \(bacnet\) firmwareNVD

Affected:< 3.5.3Fixed in:3.5.3CVE-2021-27391derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

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

Exploit Intelligence

3.26%probability of exploitation in 30 days

87thpercentile

Elevated risk: more likely to be exploited than 87% of all known CVEs.

References

Patch1

cert-portal.siemens.com

Related Vulnerabilities

Other CWE-120 (Classic Buffer Overflow) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2014-0195	Medium	6.8	100%	-	Fix
CVE-2017-7269	Critical	9.8	100%	KEV	-
CVE-2019-11043	High	8.7	99%	KEV + Ransom	Fix
CVE-2011-4862	High	10.0	95%	-	Fix
CVE-2007-5659	High	7.8	94%	KEV	Fix
CVE-2022-3786	High	7.5	91%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-04-23.