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Microsoft Issues Emergency Update for Actively Exploited WSUS Vulnerability (CVE-2025-59287)
Table of Contents
Published: November 8,2025
What Happened?
Microsoft has released an out-of-band security update to comprehensively address CVE-2025-59287,a critical remote code execution vulnerability affecting Windows Server Update Services (WSUS). Reports indicate this vulnerability is currently being exploited in the wild, prompting Microsoft to issue the update outside of its regular Patch Tuesday schedule.
The initial fix released during the October 2025 Patch Tuesday was deemed insufficient, leading to this second, more complete update.
Understanding CVE-2025-59287
What is WSUS?
Windows Server Update Services (WSUS) is a Microsoft tool designed to streamline update management within organizations. Instead of individual computers directly downloading updates from Microsoft servers, WSUS acts as a central repository. It downloads updates and then distributes them to computers on the network that connect to it. this approach conserves bandwidth and provides greater control over the update process.
Technical Details of the Vulnerability
CVE-2025-59287 is a critical vulnerability classified as a deserialization of untrusted data flaw. This means an attacker can possibly execute arbitrary code on vulnerable machines by sending a specially crafted event to the WSUS server. Crucially, no user interaction is required to trigger this vulnerability, making it particularly dangerous.
The vulnerability specifically affects Windows Server machines with the WSUS Server role enabled. ItS important to note that this role is not enabled by default.
Exploitation and Risk
Dustin Childs, head of threat awareness at Trend micro’s Zero Day Initiative, has warned that CVE-2025-59287 is wormable
between affected WSUS servers. This means a compromised WSUS server can automatically infect other vulnerable WSUS servers on the network, leading to rapid propagation of the attack. WSUS servers are considered attractive targets for attackers due to their central role in managing updates for potentially hundreds or thousands of computers.
While Microsoft states that exploitation from the internet should be impossible with proper network configuration (i.e., WSUS is not directly exposed to the internet), misconfigurations are common, and internal network breaches can provide attackers with access to vulnerable WSUS servers.
Affected Systems and Mitigation
The vulnerability affects Windows Server machines running the WSUS Server role. Administrators should immediately apply the latest out-of-band security update released by Microsoft. The update can be downloaded from the Microsoft Security Update Guide.
Verification of Patch Submission
After applying the update, verify its successful installation by checking the WSUS server logs and ensuring no errors are reported. Consider using vulnerability scanning tools to confirm the vulnerability has been remediated.
| Operating System | WSUS server Role | Mitigation |
|---|---|---|
| Windows Server (Various Versions) | enabled
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