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CVE-2021-31888

27
FAUCET Score

CVE-2021-31888 is a critical vulnerability affecting numerous Siemens APOGEE, Desigo, and TALON products, as well as the Nucleus NET and ReadyStart V3 embedded TCP/IP stacks. The vulnerability stems from improper length validation in the FTP server's "MKD/XMKD" command, leading to stack-based buffer overflows. With a CVSS score of 8.8 (High), this flaw allows for unauthenticated remote attackers to achieve Denial-of-Service and potentially Remote Code Execution with low attack complexity. While there is no evidence of active exploitation or public exploit code (Metasploit, Nuclei, ExploitDB), the vulnerability has garnered significant community discussion and media coverage, highlighting its potential impact on critical systems.

Impacted Technologies

VendorProductVersion(s)CPE
All Versions ImpactedCPE matchmatch criteria
cpe:2.3:a:siemens:nucleus_net:*:*:*:*:*:*:*:*
< 2017.02.4CPE matchmatch criteria
cpe:2.3:a:siemens:nucleus_readystart_v3:*:*:*:*:*:*:*:*
All Versions ImpactedCPE matchmatch criteria
cpe:2.3:a:siemens:nucleus_source_code:*:*:*:*:*:*:*:*
All Versions ImpactedCPE matchmatch criteria
cpe:2.3:o:siemens:apogee_modular_building_controller_firmware:*:*:*:*:*:*:*:*
All Versions ImpactedCPE matchmatch criteria
cpe:2.3:o:siemens:apogee_modular_equiment_controller_firmware:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

8.8HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
2.8
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
2.37%
Probability of exploitation in next 30 days
EPSS Percentile
82.1%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0237 is in the 81st percentile among its peer group of 17,844 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.3 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

cert-portal.siemens.com / productcert/pdf/ssa-044112.pdf
Vendor Advisory
cert-portal.siemens.com / productcert/pdf/ssa-114589.pdf
Vendor Advisory