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Vulnerability record · CVE-2025-40820 · published 9 December 2025

CVE-2025-40820: Affected products do not properly enforce TCP sequence number validation in specific scenarios but accept valu…

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.

8.7 CVSS 4.0 High EPSS 0.49% · top 60.3% CWE-940 · CWE-940 Deferred
8.7CVSS 4.0 base score
0.49%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
1References
17 Jun 2026Last modified by NVD

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.

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
https://cert-portal.siemens.com/productcert/html/ssa-915282.html

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.3CVE-2025-61932Lanscope Endpoint Manager improper origin verification allows RCELanscope Endpoint Manager (On-Premises), in both the Client program (MR) and Detection agent (DA), does not properly verify the origin of incoming re…KEVEPSS 2.8%analysed

Source: NIST National Vulnerability Database (record CVE-2025-40820), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.