CVE-2025-40820
HIGHDescription
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.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Exploit Intelligence
Low risk: more likely to be exploited than 39% of all known CVEs.
References
Related Vulnerabilities
Other CWE-940 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2025-61932 | Critical | 9.8 | 2.6% | KEV | - |
| CVE-2024-32388 | Medium | 5.3 | 1.2% | - | Fix |
| CVE-2025-23018 | Medium | 5.4 | 1.0% | - | - |
| CVE-2023-48387 | High | 8.8 | 1.0% | - | - |
| CVE-2023-3663 | High | 8.8 | 1.0% | - | Fix |
| CVE-2025-23019 | Medium | 5.4 | 1.0% | - | - |
Common questions
How do I fix CVE-2025-40820?
No published fix for CVE-2025-40820 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2025-40820 being actively exploited?
Not that we know of. CVE-2025-40820 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.48% is the estimated probability that it will be exploited in the next 30 days. That is higher than 39% of all scored CVEs.
How severe is CVE-2025-40820?
CVE-2025-40820 has a CVSS v3 base score of 7.5, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-12-09.