What is CVE-2026-20833?

CVE-2026-20833 is a medium-severity vulnerability in Microsoft Windows Server 2008, classified under Use of a Broken or Risky Cryptographic Algorithm. CVSS score: 5.5/10. Published 2026-01-13.

How severe is CVE-2026-20833?

Medium severity. CVSS v3 base score is 5.5 out of 10.

Is CVE-2026-20833 known to be exploited?

2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Vulnerability in Microsoft Windows Server 2008

CVE-2026-20833

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

Vulnerability class: POODLE (CVE-2014-3566)

Published 2026-01-13 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.005 (43.2th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 43rd percentile — 43.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: +0.000

Affected products

Microsoft Windows Server 2008 — versions r2
Microsoft Windows Server 2008 R2 Service Pack 1 — versions 6.1.7601.0
Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core Installation) — versions 6.1.7601.0
Microsoft Windows Server 2008 Service Pack 2 — versions 6.0.6003.0
Microsoft Windows Server 2008 Service Pack 2 (Server Core Installation) — versions 6.0.6003.0
Microsoft Windows Server 2012 — versions 6.2.9200.0
Microsoft Windows Server 2012 — versions r2
Microsoft Windows Server 2012 R2 — versions 6.3.9600.0
Microsoft Windows Server 2012 R2 (Server Core Installation) — versions 6.3.9600.0
Microsoft Windows Server 2012 (Server Core Installation) — versions 6.2.9200.0

Weakness classification (CWE)

CWE-327 — Use of a Broken or Risky Cryptographic Algorithm

Public proof-of-concept exploits

References

Windows Kerberos Information Disclosure Vulnerability (vendor-advisory, patch, Vendor Advisory)

Frequently asked questions

What is CVE-2026-20833?: CVE-2026-20833 is a medium-severity vulnerability in Microsoft Windows Server 2008, classified under Use of a Broken or Risky Cryptographic Algorithm. CVSS score: 5.5/10. Published 2026-01-13.
How severe is CVE-2026-20833?: Medium severity. CVSS v3 base score is 5.5 out of 10.
Is CVE-2026-20833 known to be exploited?: 2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.