CVE-2021-27391

CRITICAL
9.8
CVSS Score
Published: September 14, 2021 at 10:47 AM UTC
Updated: June 17, 2026 at 03:44 AM UTC
17 products affected across 1 vendorTalon Tc Modular (bacnet ) FirmwareApogee Pxc Compact (p2 Ethernet ) FirmwareTalon Tc Compact (bacnet ) Firmware

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Severity
CRITICAL9.8
Exploit prediction
EPSS 3%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

siemens-apogee-mbc-ppc-p2-ethernet (same device)
siemens-apogee-mec-ppc-p2-ethernet (same device)
v < 3.5.3
Affected range stops below 3.5.3, so it looks safe — our inference, not a vendor statement
siemens-apogee-pxc-bacnet-automation-controller (same device)
siemens-apogee-pxc-compact-p2-ethernet (same device)
Affected range stops below 3.5.3, so it looks safe — our inference, not a vendor statement
siemens-apogee-pxc-modular-bacnet (same device)
siemens-apogee-pxc-modular-p2-ethernet (same device)
Affected range stops below 3.5.3, so it looks safe — our inference, not a vendor statement
siemens-talon-tc-compact-bacnet (same device)
Affected range stops below 3.5.3, so it looks safe — our inference, not a vendor statement
siemens-talon-tc-modular-bacnet (same device)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (1)

SSVC — Action Prioritization

SSVCNo known exploitAutomatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

9.8CRITICALCISA-ADP
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-120

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