CVE Tools
Track your stack

CVE-2026-21249

Windows NTLM Spoofing Vulnerability

Exploitation likely. EPSS gives it a 11% chance of exploitation in the next 30 days. Fixed versions are out.

CVSS 3.13.3LowEPSS percentile96th11% chance in 30 daysCISA KEVNot listedNo confirmed exploitation
No public exploit knownFix5 products10 fixed builds listed below

Published Updated Sources: CVE.org, NVD, BDU

NVD CVE.org

What to do

Find your product and version, then upgrade to the build on the right.

  • Microsoft Windows 10 Version 1607Affected: ≥ 10.0.14393.0, < 10.0.14393.8868Upgrade to: 10.0.14393.8868Affected: ≥ 10.0.17763.0, < 10.0.17763.8389Upgrade to: 10.0.17763.8389Affected: ≥ 10.0.19044.0, < 10.0.19044.6937Upgrade to: 10.0.19044.6937Affected: ≥ 10.0.19045.0, < 10.0.19045.6937Upgrade to: 10.0.19045.6937Stated by: CVE record
  • Microsoft Windows 11 version 22H3Affected: ≥ 10.0.22631.0, < 10.0.22631.6649Upgrade to: 10.0.22631.6649Affected: ≥ 10.0.26100.0, < 10.0.26100.7840Upgrade to: 10.0.26100.7840Affected: ≥ 10.0.26200.0, < 10.0.26200.7840Upgrade to: 10.0.26200.7840Affected: ≥ 10.0.28000.0, < 10.0.28000.1575Upgrade to: 10.0.28000.1575Stated by: CVE record
  • Microsoft Windows Server 2016Affected: ≥ 10.0.14393.0, < 10.0.14393.8868Upgrade to: 10.0.14393.8868Stated by: CVE record
  • Microsoft Windows Server 2019Affected: ≥ 10.0.17763.0, < 10.0.17763.8389Upgrade to: 10.0.17763.8389Stated by: CVE record
  • Microsoft Windows Server 2022Affected: ≥ 10.0.20348.0, < 10.0.20348.4773Upgrade to: 10.0.20348.4773Affected: ≥ 10.0.25398.0, < 10.0.25398.2149Upgrade to: 10.0.25398.2149Stated by: CVE record

Versions as the sources state them. 2 more products have version data. Full version matrix after sign-in

Check it yourselfA free OpenVAS check exists for this CVE. Run it against your hosts.Is your organisation exposed?Request an assessment to establish which checks fit your systems.

What it is

From the CVE record

External control of file name or path in Windows NTLM allows an unauthorized attacker to perform spoofing locally.

In plain language

No plain-language summary for this CVE yet.

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

EPSS96th
CISA KEV

Not in the catalog. CISA has not confirmed exploitation.

Public exploits

No public exploit or proof of concept found in the sources we track.

EPSS

11% chance of exploitation activity in the next 30 days, which ranks it in the 96th percentile of scored CVEs.

Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.

Lifecycle

6 events over 135 days, from the signal feeds we watch.

  1. OpenVAS check added
  2. EPSS band changelow → moderate
  3. Patch availablerecord updated
  4. Publishedweakness classified

Affected products

And 44 more affected products. See all after sign-in

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

Scored 3.3 by NVD.

How it is reached

  • Attack Vector LocalRequires local access to the vulnerable system (e.g. local login, malicious file)
  • Attack Complexity LowNo special conditions — the attack can be reliably reproduced
  • Privileges Required NoneNo authentication required — anyone can exploit this
  • User Interaction RequiredA user must click a link, open a file, or perform some action

Scope

  • Scope UnchangedImpact is limited to the vulnerable component itself

Impact if exploited

  • Confidentiality LowSome restricted information is disclosed, but limited in scope
  • Integrity NoneNo integrity impact
  • Availability NoneNo availability impact

Weaknesses

Sources

References in the record

In the news

Watch the software you run.

My Stack ranks new CVEs for your products by real-world exploitation, so the next serious one reaches you without reading every advisory.

We'll flag the next CVE, public exploit or patch for Windows 10 Version 1607, not every advisory.