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Cybersecurity authorities including CISA and NSA, in collaboration with international partners, have issued urgent guidance to secure on-premise Microsoft Exchange Server and Windows Server Update Services (WSUS) instances. The recommendations emphasize restricting administrative access, enforcing multi-factor authentication, maintaining strict security baselines, and decommissioning end-of-life servers to mitigate ongoing threats. Organizations are urged to apply security updates promptly, enable advanced security features, and adopt zero trust principles to defend against persistent malicious activity targeting these critical Microsoft services.
Simultaneously, a newly disclosed vulnerability in WSUS, tracked as CVE-2025-59287, is being actively exploited by cybercriminals to deploy the Skuld Stealer malware. Despite Microsoft's initial and subsequent out-of-band patches, attackers have leveraged the flaw to gain remote control over WSUS servers, using legitimate tools like PowerShell and cURL for malicious purposes. The exploitation prompted CISA to add the vulnerability to its list of known exploited vulnerabilities, underscoring the urgency for organizations to implement the latest security updates and follow best practices to protect their infrastructure.
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3 events from the most recent confirmed update back to the earliest known activity.
CISA and the NSA published urgent guidance advising organizations to harden and secure WSUS and Microsoft Exchange servers. The guidance reflects official concern over the security risks and need for immediate defensive action.
Hackers were reported exploiting the WSUS vulnerability to spread the Skuld Stealer malware, indicating active abuse despite Microsoft's patch. This marked the operational use of the flaw in malware delivery.
Microsoft had already issued a security patch for a Windows Server Update Services (WSUS) vulnerability before later reporting showed attackers were still exploiting it. The patch release is referenced as preceding the observed abuse campaign.
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Microsoft released an urgent out-of-band security update to address a critical remote code execution vulnerability in Windows Server Update Services (WSUS), identified as CVE-2025-59287. The flaw was reportedly under active exploitation in the wild, prompting Microsoft to issue a comprehensive fix outside of its regular update cycle. Security advisories and industry news highlighted the severity of the vulnerability and its inclusion in the U.S. CISA Known Exploited Vulnerabilities catalog, underscoring the immediate risk to organizations relying on WSUS for patch management. The vulnerability allowed attackers to potentially execute arbitrary code on affected WSUS servers, posing a significant threat to enterprise environments. Security experts urged organizations to apply the patch without delay to mitigate the risk of compromise. The rapid response from Microsoft and the attention from security agencies reflect the critical nature of the flaw and the ongoing threat landscape targeting core infrastructure components like WSUS.
Jul 12, 2026
Microsoft Windows Server Update Services (WSUS) is affected by **CVE-2025-59287**, a critical unauthenticated remote code execution flaw with a **CVSS 9.8** score that is being actively exploited in the wild. The vulnerability stems from insecure deserialization of `AuthorizationCookie` objects handled by the `GetCookie()` endpoint, allowing a remote attacker to send crafted `POST` requests to WSUS servers exposed on ports `8530` and `8531` and execute arbitrary code as **SYSTEM**. Observed exploitation has involved WSUS-related processes such as `w3wp.exe` and `wsusservice.exe` spawning `cmd.exe` and `powershell.exe`, indicating full server compromise through the update management service. Microsoft has issued an emergency security update for affected WSUS deployments, while defenders have been urged to patch immediately, restart servers after applying fixes, and restrict inbound access to ports `8530` and `8531` or disable WSUS temporarily if patching cannot be completed at once.
Jul 24, 2026
A critical remote code execution (RCE) vulnerability was discovered in Microsoft's Update Health Tools (KB4023057), a utility designed to facilitate rapid security updates via Intune. Researchers found that a misconfiguration involving abandoned Azure blob storage allowed attackers to register a storage account and receive requests from vulnerable devices worldwide, enabling arbitrary code execution. Microsoft has since responded to the disclosure, and newer versions of the tool have addressed the issue, but devices running the original version remain at risk if not updated. Separately, a remote code execution vulnerability in Microsoft Windows Server Update Services (WSUS), tracked as CVE-2025-59287, was actively exploited by threat actors to deploy the ShadowPad backdoor malware. Attackers leveraged this flaw to gain system-level access using PowerCat and subsequently installed ShadowPad via `certutil` and `curl`. The exploitation of these vulnerabilities highlights the risks associated with update management tools and the importance of timely patching and secure configuration to prevent compromise by advanced persistent threats.
Jul 12, 2026