VulnerabilityPublished 9 Dec 2025

CVE-2025-40820: Siemens SIDOOR ATD430W · Improper Verification of Source of a Communication Channel

Affects Siemens SIDOOR ATD430WSource CVE Database V5

Not known to be exploited · CVSS 7.5 High.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 41% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

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

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

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
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: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 9 Dec 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 26 Oct 2026.

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 or the CVSS exploit maturity 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 SIDOOR ATD430W	Affected =0	Fixed in–

AI-suggested

Implement strict ingress and egress filtering on network devices to block IP packets with spoofed source addresses, reducing the attacker's ability to inject spoofed TCP packets.
Deploy network intrusion detection and prevention systems (IDS/IPS) tuned to detect anomalous TCP sequence number patterns or unusual connection resets targeting Siemens SIDOOR ATD430W devices.
Segment OT and IT networks to limit exposure of vulnerable devices to untrusted networks and reduce the attack surface.
Monitor device logs and network traffic for signs of repeated TCP connection disruptions or suspicious timing patterns indicative of exploitation attempts.
Engage with Siemens support channels to obtain early access to patches or firmware updates once available and plan for timely deployment.
Where feasible, implement redundant communication paths and failover mechanisms to maintain availability during potential DoS incidents.
Educate network administrators and security teams about this specific vulnerability to enhance detection and response capabilities.
Consider temporary disabling or restricting TCP-based services on affected devices if operationally possible until patches are applied.

Description

Affected products do not properly enforce TCP sequence number validation in specific scenarios but accept values within a broad range. This could allow an unauthenticated remote attacker e.g.to interfere with connection setup, potentially leading to a denial of service. The attack succeeds only if an attacker can inject IP packets with spoofed addresses at precisely timed moments, and it affects only TCP-based services.

Impact

For European organizations, the primary impact is potential denial of service on Siemens SIDOOR ATD430W devices, which may be deployed in industrial control systems, building automation, or critical infrastructure environments. Disruption of TCP-based services could lead to operational downtime, loss of monitoring or control capabilities, and cascading effects on dependent systems. Since the vulnerability does not affect confidentiality or integrity, data breaches are unlikely, but availability interruptions can have severe consequences in sectors such as energy, manufacturing, transportation, and public utilities. The requirement for precise packet injection and spoofing limits the threat to attackers with network proximity or advanced capabilities, reducing widespread exploitation risk. However, targeted attacks against critical infrastructure could leverage this vulnerability to cause service outages or degrade system reliability. The absence of patches means organizations must rely on network-level mitigations and monitoring until Siemens releases updates. The impact is heightened in environments where Siemens devices are integral to operational technology (OT) networks with limited redundancy or failover options.

CWE-940Improper Verification of Source of a Communication Channel (opens in a new tab)
Base weaknessOWASP Top 10 A07:2025: Authentication Failures (opens in a new tab)
The product establishes a communication channel to handle an incoming request that has been initiated by an actor, but it does not properly verify that the request is coming from the expected origin.
Architecture and Design
Use a mechanism that can validate the identity of the source, such as a certificate, and validate the integrity of data to ensure that it cannot be modified in transit using an Adversary-in-the-Middle (AITM) attack.
OWASP Cheat Sheets
OWASP Authentication (opens in a new tab)
OWASP ASVS 4.0.3
V1.14.1 (opens in a new tab)
V14.5.2 (opens in a new tab)
V14.5.3 (opens in a new tab)
Attack patterns
WebView Injection (opens in a new tab)
Connection Reset (opens in a new tab)
TCP RST Injection (opens in a new tab)
Traffic Injection (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

cert-portal.siemens.com/productcert/html/ssa-915282.html (opens in a new tab)

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 16 Dec 2025, 11:39 UTC

WeaknessesCWE-940

Technical details

References

Community reviews

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