Winsage
October 28, 2025
On October 14, 2025, a critical remote code execution (RCE) vulnerability, CVE-2025-59287, was discovered in Microsoft's Windows Server Update Services (WSUS). The vulnerability allows remote, unauthenticated attackers to execute arbitrary code with system privileges on affected servers. It was initially addressed on October 14, but the patch was insufficient, leading to an urgent out-of-band update on October 23. The U.S. Cybersecurity and Infrastructure Security Agency (CISA) added the vulnerability to its Known Exploited Vulnerabilities Catalog on October 24, indicating its immediate threat.
The vulnerability affects Microsoft Windows Server 2012, 2012 R2, 2016, 2019, 2022, and 2025, specifically on servers with the WSUS role enabled. Attackers are exploiting the vulnerability by targeting publicly exposed WSUS instances on TCP ports 8530 (HTTP) and 8531 (HTTPS). Approximately 5,500 WSUS instances have been identified as exposed to the internet. Microsoft recommends disabling the WSUS Server Role or blocking inbound traffic to the high-risk ports as temporary workarounds for organizations unable to apply the emergency patches immediately.
