CVE-2025-21418 — Windows NTLM Auth Bypass¶
Key facts
CVE-2025-21418 is a Critical vulnerability: Windows NTLM Auth Bypass. This entry ships a detection-only PoC. It is on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2025-02-11), confirming active exploitation in the wild.
Actively exploited — on the CISA KEV catalog
CVE-2025-21418 is listed on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2025-02-11), confirming exploitation in the wild. Federal remediation deadline: 2025-03-04. Prioritise patching and deploy the detection and prevention rules below.
| CVE | CVE-2025-21418 |
| Severity | Critical |
| CISA KEV | Actively exploited (added 2025-02-11) |
| Detection / prevention | — |
| PoC | poc.py |
| Source | 2025/CVE-2025-21418/ |
Details¶
Overview¶
Windows NTLM auth bypass vulnerability
Details¶
- CVE ID: CVE-2025-21418
- CVSS Score: 9.8 (Critical)
- Type: Auth Bypass
- Product: Windows NTLM
Usage¶
References¶
Frequently asked questions¶
What is CVE-2025-21418?¶
CVE-2025-21418 is a Critical vulnerability: Windows NTLM Auth Bypass. This entry ships a detection-only PoC. It is on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2025-02-11), confirming active exploitation in the wild.
How do I detect CVE-2025-21418?¶
Run the detection-only PoC included with this entry against your Docker test lab to confirm whether a target is affected; pair it with your own IDS logging.
How do I block or mitigate CVE-2025-21418?¶
Upgrade to a fixed version per the vendor advisory; the NVD record lists the affected versions. Use the included PoC to verify your remediation.
Is CVE-2025-21418 actively exploited?¶
Yes. CVE-2025-21418 is on the CISA Known Exploited Vulnerabilities (KEV) catalog, added 2025-02-11, which means it has been exploited in the wild. CISA set a federal remediation deadline of 2025-03-04. Prioritise patching and deploy the detection and prevention rules above.
For authorized security testing and research only. See the full source and NVD record.