CVE Intelligence
High Denial of service

CVE-2025-40944 — Uncontrolled Resource Consumption in Siemens SIMATIC ET 200AL IM 157-1 PN

A vulnerability has been identified in SIMATIC ET 200AL IM 157-1 PN (6ES7157-1AB00-0AB0) (All versions), SIMATIC ET 200MP IM 155-5 PN HF (6ES7155-5AA00-0AC0) (All versions >= V4.2.0), SIMATIC ET 200SP IM 155-6 MF HF (6ES7155-6MU00-0CN0) (All versions), SIMATIC ET 200SP IM 155-6 PN HA (incl. SIPLUS variants) (All versions < V1.3), SIMATIC ET 200SP IM 155-6 PN R1 (6ES7155-6AU00-0HM0) (All versions < V6.0.1), SIMATIC ET 200SP IM 155-6 PN/2 HF (6ES7155-6AU01-0CN0) (All versions >= V4.2.0 < V4.2.5), SIMATIC ET 200SP IM 155-6 PN/3 HF (6ES7155-6AU30-0CN0) (All versions < V4.2.2), SIMATIC PN/MF Coupler (6ES7158-3MU10-0XA0) (All versions), SIMATIC PN/PN Coupler (6ES7158-3AD10-0XA0) (All versions < V6.0.0), SIPLUS ET 200MP IM 155-5 PN HF (6AG1155-5AA00-2AC0) (All versions >= V4.2.0), SIPLUS ET 200MP IM 155-5 PN HF (6AG1155-5AA00-7AC0) (All versions >= V4.2.0), SIPLUS ET 200MP IM 155-5 PN HF T1 RAIL (6AG2155-5AA00-1AC0) (All versions >= V4.2.0), SIPLUS ET 200SP IM 155-6 PN HF (6AG1155-6AU01-2CN0) (All versions >= V4.2.0 < V4.2.5), SIPLUS ET 200SP IM 155-6 PN HF (6AG1155-6AU01-7CN0) (All versions >= V4.2.0 < V4.2.5), SIPLUS ET 200SP IM 155-6 PN HF T1 RAIL (6AG2155-6AU01-1CN0) (All versions >= V4.2.0 < V4.2.5), SIPLUS ET 200SP IM 155-6 PN HF TX RAIL (6AG2155-6AU01-4CN0) (All versions >= V4.2.0 < V4.2.5), SIPLUS NET PN/PN Coupler (6AG2158-3AD10-4XA0) (All versions < V6.0.0). Affected devices do not properly handle S7 protocol session disconnect requests. When receiving a valid S7 protocol Disconnect Request (COTP DR TPDU) on TCP port 102, the devices enter an improper session state. This could allow an attacker to cause the device to become unresponsive, leading to a denial-of-service condition that requires a power cycle to restore normal operation.

Published Jan 13, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: siemens

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 0.4% (30-day exploitation probability)+5
  • Technical severity (high)+6
  • Automatable exploitation (SSVC)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
0.44%
ahead of 36% of scored CVEs · Oct 14, 2026
Affects
Siemens
SIMATIC ET 200AL IM 157-1 PN and 14 more
CVSS base
7.5
High · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
None
none · proof-of-concept · active
Automatable
Yes
can an attacker script the kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Siemens SIMATIC ET 200AL IM 157-1 PN, Siemens SIMATIC ET 200MP IM 155-5 PN HF, Siemens SIMATIC ET 200SP IM 155-6 MF HF…).
  2. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
  3. No fix documented in the sources: reduce exposure and monitor the vendor advisory.
  4. Search available logs for exploit probes matching the vulnerability class (denial of service), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Siemens SIMATIC ET 200AL IM 157-1 PN versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP
Siemens SIMATIC ET 200MP IM 155-5 PN HF ≥ V4.2.0 Vulnerable CVE Program (cve.org) e CISA ADP
Siemens SIMATIC ET 200SP IM 155-6 MF HF versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP
Siemens SIMATIC ET 200SP IM 155-6 PN HA (incl. SIPLUS variants) < V1.3 Vulnerable CVE Program (cve.org) e CISA ADP
Siemens SIMATIC ET 200SP IM 155-6 PN R1 < V6.0.1 Vulnerable CVE Program (cve.org) e CISA ADP
Siemens SIMATIC ET 200SP IM 155-6 PN/2 HF ≥ V4.2.0 and < V4.2.5 Vulnerable CVE Program (cve.org) e CISA ADP
Siemens SIMATIC ET 200SP IM 155-6 PN/3 HF < V4.2.2 Vulnerable CVE Program (cve.org) e CISA ADP
Siemens SIMATIC PN/MF Coupler versions not specified by the source Vulnerable CVE Program (cve.org) e CISA ADP
Siemens SIMATIC PN/PN Coupler < V6.0.0 Vulnerable CVE Program (cve.org) e CISA ADP
Siemens SIPLUS ET 200MP IM 155-5 PN HF ≥ V4.2.0 Vulnerable CVE Program (cve.org) e CISA ADP
Siemens SIPLUS ET 200MP IM 155-5 PN HF T1 RAIL ≥ V4.2.0 Vulnerable CVE Program (cve.org) e CISA ADP
Siemens SIPLUS ET 200SP IM 155-6 PN HF ≥ V4.2.0 and < V4.2.5 Vulnerable CVE Program (cve.org) e CISA ADP
Siemens SIPLUS ET 200SP IM 155-6 PN HF T1 RAIL ≥ V4.2.0 and < V4.2.5 Vulnerable CVE Program (cve.org) e CISA ADP
Siemens SIPLUS ET 200SP IM 155-6 PN HF TX RAIL ≥ V4.2.0 and < V4.2.5 Vulnerable CVE Program (cve.org) e CISA ADP
Siemens SIPLUS NET PN/PN Coupler < V6.0.0 Vulnerable CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
8.7 CVSS 4.0 High — — productcert@siemens.com via NIST National Vulnerability Database
8.7 CVSS 4.0 High — — siemens via CVE Program (cve.org) e CISA ADP
7.5 CVSS 3.1 High 3.9 3.6 productcert@siemens.com via NIST National Vulnerability Database
7.5 CVSS 3.1 High — — siemens via CVE Program (cve.org) e CISA ADP
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (score shown at the top: productcert@siemens.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-400 · Uncontrolled Resource Consumption

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.44%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
  • Track CPU/memory spikes and availability drops correlated with request patterns.
web/proxy/WAF logsnetwork IDS/IPSresource metrics

Timeline

What happened to this CVE, newest first.

  • 2026
  • Affected products added · siemens/simatic et 200al im 157-1 pn, siemens/simatic et 200mp im 155-5 pn hf, siemens/simatic et 200sp im 155-6 mf hf,
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • SSVC assessment updated
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 13, 2026
  • CVSS changed · 7.5
    Oct 13, 2026 · NIST National Vulnerability Database
  • Source status changed · → Deferred
    Oct 13, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVE published
    Jan 13, 2026 · siemens

Source activity

Repeated readings are counted rather than listed.

  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

1 on the record

Elsewhere on this site

Siemens
every CVE for this vendor
Denial of service
same class
CWE-400
other pages naming this weakness

Related CVEs (same products)

  • CVE-2025-40820 Affected products do not properly enforce TCP sequence number validation in specific… Dec 9, 2025

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No fixed version, patch or mitigation documented.
  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2025-40944 is "Uncontrolled Resource Consumption in Siemens SIMATIC ET 200AL IM 157-1 PN", rated High. It affects SIMATIC ET 200AL IM 157-1 PN (Siemens); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.5 describes technical severity. EPSS 0.44% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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