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Critical WSUS RCE Vulnerability Exploited in the Wild

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2 unique sources, 4 articles

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A critical remote code execution (RCE) vulnerability (CVE-2025-59287) in Windows Server Update Service (WSUS) is being actively exploited in the wild. The flaw allows attackers to run malicious code with SYSTEM privileges on Windows servers with the WSUS Server role enabled. Microsoft has released out-of-band patches for all affected Windows Server versions. Cybersecurity firms have observed exploitation attempts and the presence of publicly available proof-of-concept exploit code. The vulnerability is considered potentially wormable between WSUS servers and poses a significant risk to organizations. The flaw concerns a case of deserialization of untrusted data in WSUS. The vulnerability was discovered and reported by security researchers MEOW, f7d8c52bec79e42795cf15888b85cbad, and Markus Wulftange with CODE WHITE GmbH. CISA and NSA, along with international partners, have issued guidance to secure Microsoft Exchange Server instances, including recommendations to restrict administrative access, implement multi-factor authentication, and enforce strict transport security configurations. The agencies advise decommissioning end-of-life on-premises or hybrid Exchange servers after transitioning to Microsoft 365. Sophos reported threat actors exploiting the vulnerability to harvest sensitive data from U.S. organizations across various industries, with at least 50 victims identified. The exploitation activity was first detected on October 24, 2025, a day after Microsoft issued the update. Attackers use Base64-encoded PowerShell commands to exfiltrate data to a webhook[.]site endpoint. Michael Haag of Splunk noted an alternate attack chain involving the Microsoft Management Console binary (mmc.exe) to trigger cmd.exe execution. Recently, threat actors have been exploiting CVE-2025-59287 to distribute ShadowPad malware, a modular backdoor used by Chinese state-sponsored hacking groups. Attackers used PowerCat, certutil, and curl to obtain a system shell and download ShadowPad. The malware is launched via DLL side-loading and comes with anti-detection and persistence techniques.

Timeline

  1. 24.11.2025 09:18 1 articles · 23h ago

    ShadowPad Malware Distributed via WSUS Vulnerability

    Threat actors are exploiting CVE-2025-59287 to distribute ShadowPad malware. ShadowPad is a modular backdoor used by Chinese state-sponsored hacking groups. Attackers used PowerCat, certutil, and curl to obtain a system shell and download ShadowPad. The malware is launched via DLL side-loading and comes with anti-detection and persistence techniques.

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  2. 24.10.2025 19:28 4 articles · 1mo ago

    Exploitation of Critical WSUS RCE Vulnerability (CVE-2025-59287) Observed in the Wild

    CISA and NSA, along with international partners, have issued guidance to secure Microsoft Exchange Server instances. The guidance includes recommendations to restrict administrative access, implement multi-factor authentication, and enforce strict transport security configurations. The agencies advise decommissioning end-of-life on-premises or hybrid Exchange servers after transitioning to Microsoft 365. CISA updated its alert for CVE-2025-59287, recommending organizations identify and patch vulnerable servers and monitor for threat activity. Sophos reported threat actors exploiting the vulnerability to harvest sensitive data from U.S. organizations across various industries, with at least 50 victims identified. The exploitation activity was first detected on October 24, 2025, a day after Microsoft issued the update. Attackers use Base64-encoded PowerShell commands to exfiltrate data to a webhook[.]site endpoint. Michael Haag of Splunk noted an alternate attack chain involving the Microsoft Management Console binary (mmc.exe) to trigger cmd.exe execution. Threat actors are exploiting CVE-2025-59287 to distribute ShadowPad malware, a modular backdoor used by Chinese state-sponsored hacking groups. Attackers used PowerCat, certutil, and curl to obtain a system shell and download ShadowPad. The malware is launched via DLL side-loading and comes with anti-detection and persistence techniques.

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Information Snippets

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Active Exploitation of Critical Microsoft WSUS Flaw

A critical vulnerability in Microsoft Windows Server Update Service (WSUS), CVE-2025-59287, is being actively exploited in the wild. This flaw, with a CVSS score of 9.8, allows attackers to drop malicious payloads and execute arbitrary commands on infected hosts. The vulnerability affects WSUS versions 3.32.x and was discovered by Eye Security and Huntress. The Cybersecurity and Infrastructure Security Agency (CISA) has ordered U.S. government agencies to patch the flaw, which was added to the Known Exploited Vulnerabilities catalog. Organizations using WSUS are advised to apply the out-of-band security updates provided by Microsoft to mitigate the risk of exploitation. The flaw was originally patched by Microsoft as part of its Patch Tuesday updates, but attackers have since weaponized it to deploy .NET executables and Base64-encoded PowerShell scripts. Shadowserver is tracking over 2,800 WSUS instances with default ports exposed online. The vulnerability is a deserialization of untrusted data flaw that allows unauthenticated attackers to achieve remote code execution with system privileges by sending malicious encrypted cookies to the GetCookie() endpoint. A compromised WSUS server could potentially be used to distribute malicious updates to the entire network of client computers, making it particularly dangerous for large enterprises. Huntress advised isolating network access to WSUS and blocking inbound traffic to TCP ports 8530 and 8531 as remediation steps. The out-of-band (OOB) security update KB5070881 for CVE-2025-59287 broke hotpatching on some Windows Server 2025 devices. Microsoft has released a new update, KB5070893, to address the issue without disrupting hotpatching. Administrators are advised to install this update to maintain hotpatching functionality.

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