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Windows Server 2008Operating system · Microsoft

CVE-2026-20833

MEDIUM · 5.5 CVSS v3.1 Published 2026-01-13
Fix available
A fix is available. Upgrade to 10.0.14393.8783 / 10.0.17763.8276 or later.
See remediation →
57/100
Remediation priority · Elevated
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Use of a broken or risky cryptographic algorithm in Windows Kerberos allows an authorized attacker to disclose information locally.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

This vulnerability involves the use of a weak or broken cryptographic algorithm in Windows Kerberos implementation. An authorized local attacker with valid credentials can exploit this to disclose sensitive information, likely related to Kerberos ticket encryption or key derivation.

MitigationApply the appropriate Microsoft security updates for Windows Kerberos when released. Verify Kerberos authentication functions correctly after patching in test environments before production deployment.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Windows Server 2008Operating system
Affected:all versions= r2
Windows Server 2012Operating system
Affected:all versions= r2
Windows Server 2016Operating system
Affected:< 10.0.14393.8783
Windows Server 2019Operating system
Affected:< 10.0.17763.8276
Windows Server 2022Operating system
Affected:< 10.0.20348.4648
Windows Server 2022 23h2Operating system
Affected:< 10.0.25398.2092
Windows Server 2025Operating system
Affected:< 10.0.26100.32230

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Windows Server version
    Run 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to obtain the exact Windows Server build number
    Affected if Version falls within any of these vulnerable ranges: Server 2008 (all), Server 2012 (all), Server 2016 < 10.0.14393.8783, Server 2019 < 10.0.17763.8276, Server 2022 < 10.0.20348.4648, Server 2022 23h2 < 10.0.25398.2092, Server 2025 < 10.0.26100.32230
  2. Confirm Kerberos authentication is in use
    Check if the server is joined to an Active Directory domain or run 'klist get krbtgt' to list cached Kerberos tickets
    Affected if Kerberos authentication is active and the server version is within the affected ranges above
  3. Review Kerberos encryption type configuration
    Examine registry key HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System\Kerberos\Parameters for SupportedEncryptionTypes or use 'klist tickets' to view encryption types of active tickets
    Affected if Weak or deprecated encryption types (such as DES or RC4) are enabled and the server version is vulnerable

You are affected if your Windows Server version is within the listed vulnerable build numbers and Kerberos with weak encryption types is in use on the system.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 10.0.14393.8783 / 10.0.17763.8276 / 10.0.20348.4648 or later
Fixed in 10.0.14393.878310.0.17763.827610.0.20348.4648
Interim mitigation

Apply the appropriate Microsoft security updates for Windows Kerberos when released. Verify Kerberos authentication functions correctly after patching in test environments before production deployment.

Recommended fix High confidence

Apply the latest Windows Server cumulative security update; for each affected version, the fixed build is: Server 2016 >= 10.0.14393.8783, Server 2019 >= 10.0.17763.8276, Server 2022 >= 10.0.20348.4648, Server 2022 23h2 >= 10.0.25398.2092, Server 2025 >= 10.0.26100.32230

  1. Identify the current Windows Server version by running 'winver' or 'systeminfo' in Command Prompt
  2. Determine which build version your server is running (e.g., 10.0.XXXXX.XXXX)
  3. Compare your current build against the vulnerable threshold: Server 2016 < 10.0.14393.8783, Server 2019 < 10.0.17763.8276, Server 2022 < 10.0.20348.4648, Server 2022 23h2 < 10.0.25398.2092, Server 2025 < 10.0.26100.32230
  4. If vulnerable, apply the latest Windows Security Update from Microsoft Update Catalog or Windows Update
  5. Restart the server after applying the update
  6. Verify the fix by checking the new build number meets or exceeds the fixed version thresholds above
Caveat None expected; this is a security patch for a cryptographic information disclosure vulnerability

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Windows Server 2008 Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-20833 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data