CyberSecBulletin
CVE-2025-59287Exploited in the wildNVD status: Analyzed

Microsoft Windows Server Update Service (WSUS) Deserialization of Untrusted Data

Published Updated By the CyberSecBulletin desk

CVE-2025-59287 is a critical-severity deserialization of untrusted data vulnerability in Windows Server 2012 from Microsoft, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 6.2.9200.25728 as the first without the flaw, so updating Windows Server 2012 to that release or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on October 24, 2025, which means attacks have been observed in the wild.

Patch now

Attackers are already exploiting this vulnerability, according to CISA.

What to do

  1. Update Windows Server 2012 to 6.2.9200.25728 or a later version.
  2. Update Windows Server 2012 (Server Core installation) to 6.2.9200.25728 or a later version.
  3. Update Windows Server 2012 R2 to 6.3.9600.22826 or a later version.
  4. CISA's required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
  5. Read the advisory on msrc.microsoft.com for workarounds and exact fixed builds.
  6. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
MicrosoftWindows Server 20126.2.9200.0 up to, but not including, 6.2.9200.257286.2.9200.25728
MicrosoftWindows Server 2012 (Server Core installation)6.2.9200.0 up to, but not including, 6.2.9200.257286.2.9200.25728
MicrosoftWindows Server 2012 R26.3.9600.0 up to, but not including, 6.3.9600.228266.3.9600.22826
MicrosoftWindows Server 2012 R2 (Server Core installation)6.3.9600.0 up to, but not including, 6.3.9600.228266.3.9600.22826
MicrosoftWindows Server 201610.0.14393.0 up to, but not including, 10.0.14393.852410.0.14393.8524
MicrosoftWindows Server 2016 (Server Core installation)10.0.14393.0 up to, but not including, 10.0.14393.852410.0.14393.8524
MicrosoftWindows Server 201910.0.17763.0 up to, but not including, 10.0.17763.792210.0.17763.7922
MicrosoftWindows Server 2019 (Server Core installation)10.0.17763.0 up to, but not including, 10.0.17763.792210.0.17763.7922
MicrosoftWindows Server 202210.0.20348.0 up to, but not including, 10.0.20348.429710.0.20348.4297
MicrosoftWindows Server 2022, 23H2 Edition (Server Core installation)10.0.25398.0 up to, but not including, 10.0.25398.191610.0.25398.1916
MicrosoftWindows Server 202510.0.26100.0 up to, but not including, 10.0.26100.690510.0.26100.6905
MicrosoftWindows Server 2025 (Server Core installation)10.0.26100.0 up to, but not including, 10.0.26100.690510.0.26100.6905
MicrosoftWindows Server 2022 23h2before 10.0.25398.191610.0.25398.1916

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (microsoft.com).

Official description

Deserialization of untrusted data in Windows Server Update Service allows an unauthorized attacker to execute code over a network.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Deserialization of Untrusted Data

The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.

How developers prevent this class of flaw

  • If available, use the signing/sealing features of the programming language to assure that deserialized data has not been tainted. For example, a hash-based message authentication code (HMAC) could be used to ensure that data has not been modified.
  • When deserializing data, populate a new object rather than just deserializing. The result is that the data flows through safe input validation and that the functions are safe.
  • Explicitly define a final object() to prevent deserialization.

More Deserialization of Untrusted Data vulnerabilities (CWE-502)

Timeline

  1. CVE record published.
  2. Added to CISA's Known Exploited Vulnerabilities catalogue.
  3. CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: total).
  4. Deadline for US federal agencies to remediate, set by CISA.
  5. Record last changed materially (score, affected products, status or references).

References

Technical write-ups (may include proof of concept)

Other vulnerabilities in Windows Server 2012

All Windows Server 2012 vulnerabilities

Recent Deserialization of Untrusted Data vulnerabilities

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