CVE-2025-40743

Unauthorized VNC access via insufficient password verification

Published Aug 12, 2025 · Updated Aug 13, 2025

Authentication bypass in Siemens SINUMERIK controllers allows adjacent remote attackers to gain VNC access without sufficient password verification. The VNC access service improperly validates authentication and accepts an insufficiently verified password instead of enforcing the configured credential check. Reachability requires adjacent network access to an exposed VNC service, and a successful session permits unauthorized interaction that can disclose or alter data and interrupt controller operation.

CVSS severity8.7
High
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in Siemens SINUMERIK controllers allows adjacent remote attackers to gain VNC access without sufficient password verification. The VNC access service improperly validates authentication and accepts an insufficiently verified password instead of enforcing the configured credential check. Reachability requires adjacent network access to an exposed VNC service, and a successful session permits unauthorized interaction that can disclose or alter data and interrupt controller operation.

The record

CVE
CVE-2025-40743
Published
Aug 12, 2025
Updated
Aug 13, 2025
Vendor
Siemens
Product
SINUMERIK 828D PPU.5
Classifications
CWE-288, T1210
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 12, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 13, 2025Record 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=0 <V5.25 SP1

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Siemens · SINUMERIK 828D PPU.5version=0 <V5.25 SP1
Siemens · SINUMERIK 828D PPU.4version=0 <V4.95 SP5
Siemens · SINUMERIK MCversion=0 <V1.15 SP5; version=0 <V1.25 SP1
Siemens · SINUMERIK ONEversion=0 <V6.15 SP5; version=0 <V6.25 SP1
Siemens · SINUMERIK 840D slversion=0 <V4.95 SP5

Published CVSS scores

8.7Siemens ProductCERTCVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N
8.3Siemens ProductCERTCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L

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)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-288Authentication Bypass Using an Alternate Path or Channel
T1210Exploitation of Remote Services

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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