CyberSecBulletin
CVE-2025-40743NVD status: Deferred

SINUMERIK 828D PPU.4: Authentication Bypass Using an Alternate Path or Channel

Published Updated By the CyberSecBulletin desk

CVE-2025-40743 is a high-severity authentication bypass using an alternate path or channel vulnerability in SINUMERIK 828D PPU.4 from Siemens, with a CVSS 3.1 base score of 8.3 out of 10. It can be exploited from the same local network by an unauthenticated attacker, without any action from a user. The record lists version V4.95 SP5 as the first without the flaw, so updating SINUMERIK 828D PPU.4 to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.27% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update SINUMERIK 828D PPU.4 to V4.95 SP5 or a later version.
  2. Update SINUMERIK 828D PPU.5 to V5.25 SP1 or a later version.
  3. Update SINUMERIK 840D sl to V4.95 SP5 or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
SiemensSINUMERIK 828D PPU.4before V4.95 SP5V4.95 SP5
SiemensSINUMERIK 828D PPU.5before V5.25 SP1V5.25 SP1
SiemensSINUMERIK 840D slbefore V4.95 SP5V4.95 SP5
SiemensSINUMERIK MCbefore V1.25 SP1V1.25 SP1
SiemensSINUMERIK MC V1.15before V1.15 SP5V1.15 SP5
SiemensSINUMERIK ONEbefore V6.25 SP1V6.25 SP1
SiemensSINUMERIK ONE V6.15before V6.15 SP5V6.15 SP5

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
AdjacentThe attacker must be on the same local network segment.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
LowPerformance or availability is reduced.

Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L. Scored by CNA (siemens.com).

Scoring systemScoreSeverityScored by
CVSS 4.08.7HighCNA (siemens.com)
CVSS 3.18.3HighCNA (siemens.com)

Official description

A vulnerability has been identified in SINUMERIK 828D PPU.4 (All versions < V4.95 SP5), SINUMERIK 828D PPU.5 (All versions < V5.25 SP1), SINUMERIK 840D sl (All versions < V4.95 SP5), SINUMERIK MC (All versions < V1.25 SP1), SINUMERIK MC V1.15 (All versions < V1.15 SP5), SINUMERIK ONE (All versions < V6.25 SP1), SINUMERIK ONE V6.15 (All versions < V6.15 SP5). The affected application improperly validates authentication for its VNC access service, allowing access with insufficient password verification. This could allow an attacker to gain unauthorized remote access and potentially compromise system confidentiality, integrity, or availability.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Authentication Bypass Using an Alternate Path or Channel

The product requires authentication, but the product has an alternate path or channel that does not require authentication.

How developers prevent this class of flaw

  • Funnel all access through a single choke point to simplify how users can access a resource. For every access, perform a check to determine if the user has permissions to access the resource.

More Authentication Bypass Using an Alternate Path or Channel vulnerabilities (CWE-288)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Authentication Bypass Using an Alternate Path or Channel vulnerabilities

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