CVE-2025-40820

HIGH
7.5
CVSS Score
Published: December 9, 2025 at 10:44 AM UTC
Updated: October 7, 2026 at 11:10 AM UTC
119 products affected across 1 vendorSIMATIC S7-1500-cpu 1512SP 1SIMATIC S7-1500-cpu 1510SP 1SIMATIC S7-1500-cpu 1512SPF 1

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Severity
HIGH7.5
Exploit prediction
EPSS 0.5%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < V2.0.0
Affected range stops below V2.0.0, so it looks safe — our inference, not a vendor statement
v < V2.0.0
Affected range stops below V2.0.0, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.5HIGHsiemens
Vector?

Quick Info

StatusDEFERRED
CWE
CWE-940

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