A critical remote code execution (RCE) flaw, tracked as CVE-2025-59287, has put thousands of enterprise networks at risk by exposing the Windows Server Update Service (WSUS) to active exploitation. The vulnerability, rooted in unsafe object deserialization, allows unauthenticated remote attackers to execute arbitrary code with System-level privileges — effectively granting full administrative control over targeted Windows servers. Because WSUS manages how updates are distributed across enterprise networks, a compromised instance can give attackers the ability to manipulate software updates, deploy malware, or hijack patch pipelines at scale.

Following the discovery of in-the-wild attacks, Microsoft released out-of-band security updates, emphasizing the urgency of immediate patch deployment. Despite this, researchers from Eye Security and the Dutch National Cyber Security Centre (NCSC) have confirmed active exploitation shortly after a Proof-of-Concept (PoC) exploit was made public. The vulnerability impacts multiple Windows Server versions — including 2012, 2016, 2019, 2022, and 2025 — and requires only that the WSUS Server Role be enabled for successful compromise.

Security firm HawkTrace was the first to publish detailed technical analysis and a working PoC, demonstrating how attackers can trigger the deserialization flaw by sending a crafted event to a vulnerable WSUS instance. Within hours of these details going public, threat actors began leveraging the exploit in real-world attacks, highlighting the alarming speed of vulnerability weaponization in modern threat landscapes.

As of Eye Security’s latest findings, more than 2,500 WSUS servers worldwide remain exposed and unpatched. Microsoft’s official guidance urges immediate installation of both the initial and follow-up out-of-band patches, while administrators unable to patch immediately are advised to disable the WSUS Server Role as a temporary mitigation to close the attack vector.

This incident underscores the critical importance of rapid patch management, proactive monitoring, and layered defenses for infrastructure components that underpin enterprise security ecosystems. The exploitation of CVE-2025-59287 is a stark reminder that attackers move faster than ever — and that every hour between disclosure and patching can mean the difference between defense and disaster.

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