CVE-2021-42027Network attack vector

Server impersonation via improper certificate validation

Published Dec 14, 2021 · Updated Aug 4, 2024

Improper certificate validation in Siemens SINUMERIK Edge before 3.2 allows man-in-the-middle attackers to spoof trusted servers. Its TLS client accepts a server certificate without properly validating it when establishing an outbound connection. The attacker must control the communication path; successful exploitation permits server impersonation and modification or disclosure of exchanged data.

CVSS severity7.4
High
EPSS probability0.48%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in Siemens SINUMERIK Edge before 3.2 allows man-in-the-middle attackers to spoof trusted servers. Its TLS client accepts a server certificate without properly validating it when establishing an outbound connection. The attacker must control the communication path; successful exploitation permits server impersonation and modification or disclosure of exchanged data.

The record

CVE
CVE-2021-42027
Published
Dec 14, 2021
Updated
Aug 4, 2024
Vendor
Siemens
Product
SINUMERIK Edge
Classifications
CWE-295, CAPEC-475, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 14, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=All versions < V3.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Siemens · SINUMERIK Edgeversion=All versions < V3.2

Published CVSS scores

7.4NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
5.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-295Improper Certificate Validation
CAPEC-475Signature Spoofing by Improper Validation
T1557Adversary-in-the-Middle

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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