CVE-2025-40743VulnerabilityPublished 12 Aug 2025Updated 13 Aug 2025

CVE-2025-40743: Siemens SINUMERIK 828D PPU.4 · Authentication Bypass Using an Alternate Path or Channel

Affects Siemens SINUMERIK 828D PPU.4Source CVE Database V5

Not known to be exploited · CVSS 8.3 High.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

8.3High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 15% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Adjacent
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Adjacent: The vulnerable component is bound to the network stack, but the attack is limited at the protocol level to a logically adjacent topology. This can mean an attack must be launched from the same shared physical (e.g., Bluetooth or IEEE 802.11) or logical (e.g., local IP subnet) network, or from within a secure or otherwise limited administrative domain (e.g., MPLS, secure VPN to an administrative network zone).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 12 Aug 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-26.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Siemens SINUMERIK 828D PPU.4	Affected =0	Fixed in–

AI-suggested

European organizations should prioritize the following specific actions: 1) Immediate identification and inventory of all Siemens SINUMERIK devices in their environment, including versions and patch levels. 2) Apply Siemens-provided patches or upgrade to the fixed versions (e.g., V4.95 SP5 or later for 828D PPU.4) as soon as they become available. 3) Restrict network access to VNC services on these devices by implementing network segmentation and firewall rules to limit access only to trusted management networks or VPNs. 4) Disable VNC access if not required for operational purposes. 5) Implement strong network monitoring and anomaly detection focused on unusual access patterns to these control systems. 6) Enforce strict access control policies and multi-factor authentication for remote management interfaces where possible. 7) Conduct regular security audits and penetration testing of industrial control networks to detect potential exploitation attempts. 8) Collaborate with Siemens support and cybersecurity teams for guidance and updates. These measures go beyond generic advice by emphasizing network-level controls, device inventory, and operational security tailored to industrial environments.

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.

Impact

For European organizations, particularly those in manufacturing, automotive, aerospace, and heavy industry sectors that rely on Siemens SINUMERIK CNC systems, this vulnerability poses a substantial risk. Unauthorized access to CNC controllers can lead to operational disruptions, production downtime, and compromised product quality. Confidentiality breaches could expose proprietary manufacturing processes or intellectual property. Integrity violations could result in malicious alteration of machine instructions, causing defective products or physical damage to machinery, which may also pose safety hazards. Availability impact is rated lower but could still occur if attackers disrupt control systems. Given the critical role of industrial automation in European manufacturing supply chains, exploitation could have cascading effects on production schedules and economic output. Additionally, regulatory compliance frameworks such as NIS2 and GDPR may impose reporting obligations and penalties if such incidents lead to data breaches or operational failures. The lack of known exploits in the wild currently reduces immediate risk, but the high severity and ease of exploitation without authentication make proactive mitigation essential.

CWE-288Authentication Bypass Using an Alternate Path or Channel (opens in a new tab)
Base weaknessOWASP Top 10 A07:2025: Authentication Failures (opens in a new tab)
The product requires authentication, but the product has an alternate path or channel that does not require authentication.
Architecture and Design
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.
OWASP Cheat Sheets
OWASP Authentication (opens in a new tab)
OWASP ASVS 4.0.3
V1.2.3 (opens in a new tab)
V1.2.2 (opens in a new tab)
V1.2.4 (opens in a new tab)
Attack patterns
Directory Indexing (opens in a new tab)
Exploitation of Thunderbolt Protection Flaws (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

cert-portal.siemens.com/productcert/html/ssa-177847.html (opens in a new tab)

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 20 Aug 2025, 01:58 UTC

WeaknessesCWE-288

Technical details

References

Community reviews

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