CVE-2026-20833

Service-account password disclosure via RC4 Kerberos tickets

Published Jan 13, 2026 · Updated Jan 13, 2026

Weak Kerberos encryption in Microsoft Windows Server allows local users to recover service-account passwords from RC4 service tickets. The KDC issues service tickets using RC4 when service-account encryption settings are absent or permit legacy types, exposing crackable ticket material. A low-privileged domain user with a valid ticket-granting ticket can request those tickets and perform offline password recovery.

CVSS severity5.5
Medium
EPSS probability0.54%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Weak Kerberos encryption in Microsoft Windows Server allows local users to recover service-account passwords from RC4 service tickets. The KDC issues service tickets using RC4 when service-account encryption settings are absent or permit legacy types, exposing crackable ticket material. A low-privileged domain user with a valid ticket-granting ticket can request those tickets and perform offline password recovery.

The record

CVE
CVE-2026-20833
Published
Jan 13, 2026
Updated
Jan 13, 2026
Vendor
Microsoft
Product
Windows Server 2019
Classifications
CWE-327, T1558.003
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 13, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 13, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10.0.17763.0 <10.0.17763.8276

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Microsoft · Windows Server 2019version=10.0.17763.0 <10.0.17763.8276
Microsoft · Windows Server 2025 (Server Core installation)version=10.0.26100.0 <10.0.26100.32230
Microsoft · Windows Server 2016 (Server Core installation)version=10.0.14393.0 <10.0.14393.8783
Microsoft · Windows Server 2012 (Server Core installation)version=6.2.9200.0 <6.2.9200.25868
Microsoft · Windows Server 2012version=6.2.9200.0 <6.2.9200.25868
Microsoft · Windows Server 2008 R2version=6.1.7601.0 <6.1.7601.28117
Microsoft · Windows Server 2022, 23H2 Edition (Server Core installation)version=10.0.25398.0 <10.0.25398.2092
Microsoft · Windows Server 2016version=10.0.14393.0 <10.0.14393.8783
Microsoft · Windows Server 2012 R2 (Server Core installation)version=6.3.9600.0 <6.3.9600.22968
Microsoft · Windows Server 2019 (Server Core installation)version=10.0.17763.0 <10.0.17763.8276
Microsoft · Windows Server 2008version=6.0.6003.0 <6.0.6003.23717
Microsoft · Windows Server 2022version=10.0.20348.0 <10.0.20348.4648
Microsoft · Windows Server 2025version=10.0.26100.0 <10.0.26100.32230
Microsoft · Windows Server 2012 R2version=6.3.9600.0 <6.3.9600.22968

Published CVSS scores

5.5MicrosoftCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-327Use of a Broken or Risky Cryptographic Algorithm
T1558.003Steal or Forge Kerberos Tickets: Kerberoasting

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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