Windows Kerberos RC4 Service Ticket Information Disclosure
CVE-2026-20833 is an information disclosure vulnerability in Windows Kerberos caused by continued use of weak or legacy cryptographic algorithms, specifically RC4, during Kerberos service ticket issuance for accounts that do not have explicit Active Directory encryption type settings. Microsoft states that an authorized attacker can obtain service tickets encrypted with weak algorithms such as RC4 and perform offline attacks to recover service account passwords. The issue affects Kerberos Key Distribution Center behavior on Windows domain controllers when issuing service tickets. Microsoft’s mitigation guidance ties the fix to changing the default DefaultDomainSupportedEncTypes behavior so that, for accounts lacking an explicit msds-SupportedEncryptionTypes attribute, only AES-SHA1-encrypted tickets are supported by default.
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Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
If you can’t patch tonight, do this now.
Remediation
Patch, then assume compromise.
Exploits
No valid public exploits. Mallory filtered out 1 candidate as fakes, detection scripts, or README-only repos.
All candidate exploits were filtered out by Mallory's validation.
Affected products & vendors
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
7 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A vulnerability associated with the Kerberos protocol in Windows Server 2025 that is addressed by changing the default DefaultDomainSupportedEncTypes value to AES-SHA1 for accounts without explicit Active Directory encryption type definitions.
A vulnerability related to Kerberos KDC usage of RC4 for service account ticket issuance, addressed by changing default encryption behavior to leverage AES-SHA1 when explicit encryption types are not defined.
Kerberos認証に関する脆弱性。Microsoftは段階的にRC4を廃止することで影響低減/対処を進めるとしている（KBガイダンスあり）。
Windows Active Directory ドメイン コントローラーの Kerberos において、RC4 などのレガシ暗号で発行されたサービスチケットを攻撃者が入手できると、オフライン解析によりサービスアカウントのパスワード回復につながり得る情報漏えい/弱暗号起因の脆弱性。更新により既定の暗号スイートを AES-SHA1 のみに寄せ、段階的に強制(ブロック)へ移行する。
The version that knows your environment.
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Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.