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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.
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CSIRT.SK published an alert describing CVE-2025-59287 as a critical actively exploited WSUS vulnerability with CVSS 9.8, caused by insecure deserialization in AuthorizationCookie objects handled by the GetCookie() endpoint. The advisory also recommended restricting inbound traffic to ports 8530 and 8531 or disabling WSUS if patching was not possible.
Attackers were observed actively exploiting exposed Windows Server Update Services servers by sending crafted POST requests to ports 8530 and 8531. Observed abuse included w3wp.exe and wsusservice.exe launching cmd.exe and powershell.exe, indicating code execution as SYSTEM.
Microsoft released an emergency update for the critical WSUS remote code execution vulnerability CVE-2025-59287 and advised administrators to patch affected servers and restart them.
The Dutch NCSC reported that a trusted partner observed exploitation of CVE-2025-59287 and raised its assessment to High/High, citing high likelihood of exploitation and high potential impact. It urged organizations to apply the emergency update and avoid exposing WSUS directly to the public internet.
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Microsoft has released emergency out-of-band security updates to address a critical remote code execution (RCE) vulnerability in Windows Server Update Services (WSUS), tracked as CVE-2025-59287. The flaw, rated CVSS 9.8, allows unauthenticated attackers to exploit unsafe deserialization in the WSUS AuthorizationCookie mechanism, enabling arbitrary code execution with SYSTEM privileges. Proof-of-concept exploit code for this vulnerability is publicly available, increasing the urgency for organizations to patch affected systems immediately. The vulnerability affects only Windows servers with the WSUS Server Role enabled, and Microsoft has provided security updates for all supported Windows Server versions, along with workarounds for those unable to patch immediately. Security researcher Batuhan Er from HawkTrace detailed that the vulnerability arises from the unsafe deserialization of AuthorizationCookie objects sent to the `GetCookie()` endpoint, where encrypted cookie data is decrypted and deserialized without proper type validation. This flaw exposes WSUS servers to remote, unauthenticated attacks that require no user interaction and could potentially be wormable between WSUS servers. Microsoft strongly advises administrators to install the provided patches or apply recommended mitigations to prevent exploitation of this critical vulnerability.
Jun 29, 2026
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
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