CVE record · CVE-2025-40820

Affected products do not properly enforce TCP sequence number validation in specific scenarios but accept values within a broad range.

CVSS 8.7 HighEPSS 0.0049 · 42nd percentile

Published by the CVE Program (CNA: siemens) at 9 Dec 2025, 10:44 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it.

Affected products, as the CNA wrote them
Vendor	Product	Versions
Siemens	SIDOOR ATD430W	affected before * custom Other versions: unknown
Siemens	SIDOOR ATE530G COATED	affected before * custom Other versions: unknown
Siemens	SIDOOR ATE530S COATED	affected before * custom Other versions: unknown
Siemens	SIMATIC CFU DIQ	affected before V2.0.0 custom Other versions: unknown
Siemens	SIMATIC CFU PA	affected before V2.0.0 custom Other versions: unknown
Siemens	SIMATIC CFU PA	affected before V2.0.0 custom Other versions: unknown
Siemens	SIMATIC ET 200AL IM 157-1 PN	affected before * custom Other versions: unknown
Siemens	SIMATIC ET 200clean, CM 8x IO-Link	affected before * custom Other versions: unknown
Siemens	SIMATIC ET 200clean, DI 16x24VDC	affected before * custom Other versions: unknown
Siemens	SIMATIC ET 200clean, DIQ 16x24VDC/0,5A	affected before * custom Other versions: unknown
Siemens	SIMATIC ET 200eco PN, AI 8xRTD/TC, M12-L	affected V5.1.1 to before * custom Other versions: unknown
Siemens	SIMATIC ET 200eco PN, CM 4x IO-Link, M12-L	affected V5.1.1 to before * custom Other versions: unknown
Siemens	SIMATIC ET 200eco PN, CM 8x IO-Link, M12-L	affected V5.1.1 to before * custom Other versions: unknown
Siemens	SIMATIC ET 200eco PN, CM 8x IO-Link, M12-L	affected V5.1.1 to before * custom Other versions: unknown
Siemens	SIMATIC ET 200eco PN, DI 16x24VDC, M12-L	affected V5.1.1 to before * custom Other versions: unknown
Siemens	SIMATIC ET 200eco PN, DI 8x24VDC, M12-L	affected V5.1.1 to before * custom Other versions: unknown
Siemens	SIMATIC ET 200eco PN, DIQ 16x24VDC/2A, M12-L	affected V5.1.1 to before * custom Other versions: unknown
Siemens	SIMATIC ET 200eco PN, DQ 8x24VDC/0,5A, M12-L	affected V5.1.1 to before * custom Other versions: unknown
Siemens	SIMATIC ET 200eco PN, DQ 8x24VDC/2A, M12-L	affected V5.1.1 to before * custom Other versions: unknown
Siemens	SIMATIC ET 200MP IM 155-5 PN HF	affected V4.2.0 to before * custom Other versions: unknown
Siemens	SIMATIC ET 200pro IM 154-8 PN/DP CPU	affected before * custom Other versions: unknown
Siemens	SIMATIC ET 200pro IM 154-8F PN/DP CPU	affected before * custom Other versions: unknown
Siemens	SIMATIC ET 200pro IM 154-8FX PN/DP CPU	affected before * custom Other versions: unknown
Siemens	SIMATIC ET 200S IM 151-8 PN/DP CPU	affected before * custom Other versions: unknown
Siemens	SIMATIC ET 200S IM 151-8F PN/DP CPU	affected before * custom Other versions: unknown
Siemens	SIMATIC ET 200SP CPU 1510SP F-1 PN	affected before * custom Other versions: unknown
Siemens	SIMATIC ET 200SP CPU 1510SP-1 PN	affected before * custom Other versions: unknown
Siemens	SIMATIC ET 200SP CPU 1512SP F-1 PN	affected before * custom Other versions: unknown
Siemens	SIMATIC ET 200SP CPU 1512SP-1 PN	affected before * custom Other versions: unknown
Siemens	SIMATIC ET 200SP IM 155-6 MF HF	affected before * custom Other versions: unknown
Siemens	SIMATIC ET 200SP IM 155-6 PN HA (incl. SIPLUS variants)	affected before V1.3 custom Other versions: unknown
Siemens	SIMATIC ET 200SP IM 155-6 PN HF	affected V4.2.0 to before * custom Other versions: unknown
Siemens	SIMATIC ET 200SP IM 155-6 PN/2 HF	affected V4.2.0 to before * custom Other versions: unknown
Siemens	SIMATIC ET 200SP IM 155-6 PN/3 HF	affected V4.2.0 to before * custom Other versions: unknown
Siemens	SIMATIC PN/MF Coupler	affected before * custom Other versions: unknown
Siemens	SIMATIC PN/PN Coupler	affected before V6.0.0 custom Other versions: unknown
Siemens	SIMATIC Power Line Booster PLB, Base Module	affected before * custom Other versions: unknown
Siemens	SIMATIC Power Line Booster PLB, Modem Module ST	affected before * custom Other versions: unknown
Siemens	SIMATIC S7-1200 CPU 1211C AC/DC/Rly	affected before V4.4.0 custom Other versions: unknown
Siemens	SIMATIC S7-1200 CPU 1211C DC/DC/DC	affected before V4.4.0 custom Other versions: unknown

And 131 more products. The full list is on the CVE record.

Identifiers: CVE-2025-40820
CNA: siemens
Weakness (CWE): CWE-940
Tags: Siemens SIDOOR ATD430W
Siemens SIDOOR ATE530G COATED
Siemens SIDOOR ATE530S COATED
Siemens SIMATIC CFU DIQ
Siemens SIMATIC CFU PA
Siemens SIMATIC ET 200AL IM 157-1 PN
Siemens SIMATIC ET 200clean, CM 8x IO-Link
Siemens SIMATIC ET 200clean, DI 16x24VDC
CWE-940
Published: 9 Dec 2025
Updated: 9 Dec 2025

Not analysed yet

We haven’t published our own analysis of this CVE. If a person reviews it, this page will say what’s affected and what has to be true for it to matter.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
7.5	High	3.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H	CNA (siemens)
8.7	High	4.0	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N	CNA (siemens)Used for this record

CISA KEV Not listed.
EPSS 0.0049, the 42nd percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

This record came from the full history of the CVE Program, published 9 Dec 2025. New records show when each source confirmed them.

Sources

References from the CNA

cert-portal.siemens.com/productcert/html/ssa-915282.html

Facts on this page come from the CVE List as the CNA published them, with CVSS from the sources named above, CISA KEV and FIRST EPSS. Vendors, products and versions are shown as the CNA wrote them. We don’t reproduce the CVE’s description.