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Fencer Vulns
critical 9.8

CVE-2021-27391 json

A vulnerability has been identified in APOGEE MBC (PPC) (P2 Ethernet) (All versions >= V2.6.3), APOGEE MEC (PPC) (P2 Ethernet) (All version…

published 2021-09-14 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-14146

cvss
9.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
3.4%
EPSS 3.4% chance of exploitation in 30 days, percentile 88%
public exploits
0
none known

Summary

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.

Patch / fix

  • siemens apogee_pxc_bacnet_automation_controller_firmware 3.5.3
  • siemens apogee_pxc_modular_(bacnet)_firmware 3.5.3
  • siemens talon_tc_compact_(bacnet)_firmware 3.5.3
  • siemens talon_tc_modular_(bacnet)_firmware 3.5.3

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

cisa ICSA-21-257-07 updated cvss 9.8

Siemens APOGEE and TALON

  • Siemens APOGEE MBC (PPC) (P2 Ethernet) >=V2.6.3 Siemens APOGEE MEC (PPC) (P2 Ethernet) >=V2.6.3
    affected: mitigation, no fix available
  • Siemens APOGEE PXC Compact (BACnet) <V3.5.3
    affected: fixed in V3.5.3, mitigation
  • Siemens APOGEE PXC Compact (P2 Ethernet) >=V2.8
    affected: mitigation, no fix available
  • Siemens APOGEE PXC Modular (BACnet) <V3.5.3
    affected: fixed in V3.5.3, mitigation
  • Siemens APOGEE PXC Modular (P2 Ethernet) >=V2.8
    affected: mitigation, no fix available
  • Siemens TALON TC Compact (BACnet) <V3.5.3 Siemens TALON TC Modular (BACnet) <V3.5.3
    affected: fixed in V3.5.3, mitigation

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
total
Assessed
18 mo ago

Exploit prediction

3.37% chance of exploitation in the next 30 days, higher than 88% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 10.0 AV:N/AC:L/Au:N/C:C/I:C/A:C

Affected products

  • Siemens APOGEE MBC (PPC) (P2 Ethernet)
  • Siemens APOGEE MEC (PPC) (P2 Ethernet)
  • Siemens APOGEE PXC Compact (BACnet)
  • Siemens APOGEE PXC Compact (P2 Ethernet)
  • Siemens APOGEE PXC Modular (BACnet)
  • Siemens APOGEE PXC Modular (P2 Ethernet)
  • Siemens TALON TC Compact (BACnet)
  • Siemens TALON TC Modular (BACnet)

Classification

Weakness
  • CWE-120 Buffer Copy without Checking Size of Input

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.