CVE-2025-59287 Microsoft Windows Server Update Service (WSUS) Deserialization of Untrusted Data Vulnerability
Microsoft Windows Server Update Service (WSUS) contains a deserialization of untrusted data vulnerability that allows for remote code execution.
From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.
Should You Worry?
- CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 24 Oct 2025.
- Rated Critical severity (CVSS 9.8, scored by Vendor).
- It has been in the catalogue for 378 days. Systems still unpatched now have almost certainly been scanned for it.
What It Is
Deserialization of untrusted data in Windows Server Update Service allows an unauthorized attacker to execute code over a network.
Affected Versions
| Product | Versions |
|---|---|
| Microsoft Windows Server 2012 | 6.2.9200.0 to before 6.2.9200.25728 |
| Microsoft Windows Server 2012 (Server Core installation) | 6.2.9200.0 to before 6.2.9200.25728 |
| Microsoft Windows Server 2012 R2 | 6.3.9600.0 to before 6.3.9600.22826 |
| Microsoft Windows Server 2012 R2 (Server Core installation) | 6.3.9600.0 to before 6.3.9600.22826 |
| Microsoft Windows Server 2016 | 10.0.14393.0 to before 10.0.14393.8524 |
| Microsoft Windows Server 2016 (Server Core installation) | 10.0.14393.0 to before 10.0.14393.8524 |
From the public CVE record, as supplied by the vendor. Always confirm against the vendor advisory.
What To Do Now
- 1
Find it
Search your asset inventory and external attack surface for Microsoft Windows. Include cloud images, appliances and anything a supplier runs for you.
Attack Surface Management - 2
Fix it
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Vulnerability Management - 3
Hunt for compromise
If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.
Incident Response - 4
Prove it is fixed
Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.
Penetration Testing
The Compliance Clock
General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.
Not Sure If You Are Exposed?
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