CriticalCVE-2025-59287

    Windows Server Update Service (WSUS) Remote Code Execution Vulnerability (CVE-2025-59287)

    Published In CISA KEV since Sources: pwn.watch, SingCERT, CVE.org, Msrc Update Guide, Schneider Electric, CERT-EU

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    What is affected, what to do

    The vulnerability CVE-2025-59287 allows for remote code execution (RCE) due to deserialization of untrusted data in the Microsoft Windows Server Update Service (WSUS). An unauthenticated attacker can execute code over the network, gaining full control of the affected system. This vulnerability is actively exploited in the wild and has been observed in ransomware campaigns since October 2025. Affected products include various versions of Windows Server, such as 2012, 2016, 2019, 2022, and 2025. Immediate patching to the latest versions is critical to ensure security.

    The vulnerability is being actively exploited; treat it as a priority. Update Microsoft Windows Server 2012 to version 6.2.9200.25728, Microsoft Windows Server 2012 (Server Core installation) to version 6.2.9200.25728, Microsoft Windows Server 2012 R2 to version 6.3.9600.22826. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Microsoft Windows Server 2012 lt 6.2.9200.0..6.2.9200.25728
    • Microsoft Windows Server 2012 (Server Core installation) lt 6.2.9200.0..6.2.9200.25728
    • Microsoft Windows Server 2012 R2 lt 6.3.9600.0..6.3.9600.22826
    • Microsoft Windows Server 2012 R2 (Server Core installation) lt 6.3.9600.0..6.3.9600.22826
    • Microsoft Windows Server 2016 lt 10.0.14393.0..10.0.14393.8524
    • Microsoft Windows Server 2016 (Server Core installation) lt 10.0.14393.0..10.0.14393.8524
    • Microsoft Windows Server 2019 lt 10.0.17763.0..10.0.17763.7922
    • Microsoft Windows Server 2019 (Server Core installation) lt 10.0.17763.0..10.0.17763.7922
    • Microsoft Windows Server 2022 lt 10.0.20348.0..10.0.20348.4297
    • Microsoft Windows Server 2022, 23H2 Edition (Server Core installation) lt 10.0.25398.0..10.0.25398.1916
    • Microsoft Windows Server 2025 lt 10.0.26100.0..10.0.26100.6905
    • Microsoft Windows Server 2025 (Server Core installation) lt 10.0.26100.0..10.0.26100.6905
    Fixed in
    • Microsoft Windows Server 2012 6.2.9200.25728
    • Microsoft Windows Server 2012 (Server Core installation) 6.2.9200.25728
    • Microsoft Windows Server 2012 R2 6.3.9600.22826
    • Microsoft Windows Server 2012 R2 (Server Core installation) 6.3.9600.22826
    • Microsoft Windows Server 2016 10.0.14393.8524
    • Microsoft Windows Server 2016 (Server Core installation) 10.0.14393.8524
    • Microsoft Windows Server 2019 10.0.17763.7922
    • Microsoft Windows Server 2019 (Server Core installation) 10.0.17763.7922
    • Microsoft Windows Server 2022 10.0.20348.4297
    • Microsoft Windows Server 2022, 23H2 Edition (Server Core installation) 10.0.25398.1916
    • Microsoft Windows Server 2025 10.0.26100.6905
    • Microsoft Windows Server 2025 (Server Core installation) 10.0.26100.6905

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    9.8

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: pwn.watch, SingCERT, CVE.org, Msrc Update Guide, Schneider Electric, CERT-EU

    99.98 %

    EPSS score

    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.

    Source: FIRST EPSS, percentile 99.98

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    240.35 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploitedSource: VulnCheck KEV (opens in a new tab) How we classify
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    9.8 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    9.8
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    99.98 %
    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    99.98
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CISA assessment (SSVC)
    Exploitation: active · automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 25 October 2025
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-502

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw is network-reachable without authentication or user interaction and yields SYSTEM-level code execution on a server that every managed endpoint trusts. Its exploitation likelihood sits at the very top of the scale. A public proof-of-concept appeared shortly after the initial Patch Tuesday fix, and Microsoft had to ship an out-of-band update. Attackers are mass-scanning for reachable 8530/8531 and opening with reconnaissance and data exfiltration. CISA does not currently flag ransomware use, but the foothold is ideal for later lateral movement or supply-chain abuse. Treat internet-exposed WSUS as an emergency (patch or shut down, then run a forensic review), and internally reachable WSUS as top priority within 24 hours.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Inventory: Identify every Windows Server with the WSUS role installed, e.g. Get-WindowsFeature -Name UpdateServices | Where Installed. Only hosts with the WSUS role enabled are affected, but they are affected regardless of where they sit in the network.
      • Patch and reboot: Install Microsoft's security update for CVE-2025-59287. Minimum fixed builds: Server 2012 ≥ 6.2.9200.25728, 2012 R2 ≥ 6.3.9600.22826, 2016 ≥ 10.0.14393.8524, 2019 ≥ 10.0.17763.7922. Look up the KB number in the Microsoft (MSRC) advisory, and check newer Server releases there as well. Verify the build after the reboot.
      • If you cannot patch now: Block inbound TCP 8530 (HTTP) and 8531 (HTTPS) in the host firewall, or temporarily disable the WSUS role. Both options halt update distribution, so record either one as an explicit risk decision.
      • Remove internet exposure: Scan your external ranges, or check Shodan/Censys, for reachable 8530/8531. Pull any exposed server off the network immediately and treat it as potentially compromised.
      • Compromise assessment: For exposed or late-patched WSUS hosts, preserve IIS logs, process telemetry and egress logs from mid-October 2025 onward (see Detection rules) before you reimage.
      • Rotate credentials: If you suspect compromise, rotate service accounts, local admin accounts and any domain credentials cached on the host. WSUS servers typically run with high privileges and are trusted by every managed client.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Allow 8530/8531 only from defined client VLANs and from upstream/downstream WSUS servers. Drop all other sources at the perimeter and segment firewalls, and never NAT or port-forward WSUS to the internet.
      • Egress filtering: Restrict WSUS outbound traffic to an allowlist of Microsoft Update endpoints. In particular, block paste, webhook and tunnelling services (e.g. webhook.site, ngrok, Cloudflare tunnels).
      • IPS/WAF: Enable signatures for SOAP POSTs to /ClientWebService/Client.asmx (GetCookie carrying an oversized or oddly encoded AuthorizationCookie) and to /ReportingWebService/ReportingWebService.asmx containing .NET serialisation markers (the AAEAAAD///// BinaryFormatter Base64 prefix). Search your vendor's Suricata/Snort rulesets for CVE-2025-59287.
      • Endpoint hardening: Use EDR, AppLocker or WDAC to block or alert on cmd.exe and powershell.exe spawned by w3wp.exe (WsusPool) or wsusservice.exe.
      • Least privilege: Classify WSUS servers as Tier-0/1 assets, prohibit interactive Domain Admin logons, and manage local admin passwords with LAPS.
      • Architecture: Where feasible, shrink the WSUS footprint or move to Intune/Windows Update for Business. Every WSUS server is a potential channel for pushing tampered updates.

    3. Runbook step 3

      Detection rules

      • Process ancestry (Sysmon EID 1 / Security 4688): w3wp.exe with WsusPool in its command line, or wsusservice.exe, spawning cmd.exe, powershell.exe, whoami.exe, net.exe or ipconfig.exe. KQL: DeviceProcessEvents | where InitiatingProcessFileName in~ ("w3wp.exe","wsusservice.exe") and FileName in~ ("cmd.exe","powershell.exe","pwsh.exe")
      • IIS logs (C:\inetpub\logs\LogFiles): POSTs to Client.asmx or ReportingWebService.asmx from sources outside your client ranges, or unusual bursts and response sizes. Sigma shape: cs-uri-stem|contains: 'Client.asmx' AND c-ip NOT IN client_ranges.
      • Application log / SoftwareDistribution.log: .NET exceptions referencing System.Runtime.Serialization, BinaryFormatter or SoapFormatter, and Windows Server Update Services events reporting deserialisation errors.
      • Network (Zeek/Suricata/proxy): WSUS host making outbound HTTPS connections to non-Microsoft destinations, especially webhook.site or newly registered domains, shortly after inbound 8530/8531 sessions. SPL: index=proxy src=<wsus> NOT dest_domain IN ("*.microsoft.com","*.windowsupdate.com")
      • Post-exploitation: Encoded PowerShell (-enc), domain reconnaissance (net user /domain, nltest), and new service creation (EID 7045/4697) on WSUS hosts.

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    Deserialization of untrusted data in Windows Server Update Service allows an unauthorized attacker to execute code over a network.

    Source: pwn.watch, CSA/SingCERT, NVD (NIST), Microsoft Security Update Guide, CISA KEV Catalog, CVE.org (MITRE), schneider_csaf, cvelistv5, certeu_advisory

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    MicrosoftWindows Server 2012
    • 6.2.9200.0 – < 6.2.9200.25728
    • 6.2.9200.25728
    MicrosoftWindows Server 2012 (Server Core installation)
    • 6.2.9200.0 – < 6.2.9200.25728
    • 6.2.9200.25728
    MicrosoftWindows Server 2012 R2
    • 6.3.9600.0 – < 6.3.9600.22826
    • 6.3.9600.22826
    MicrosoftWindows Server 2012 R2 (Server Core installation)
    • 6.3.9600.0 – < 6.3.9600.22826
    • 6.3.9600.22826
    MicrosoftWindows Server 2016
    • 10.0.14393.0 – < 10.0.14393.8524
    • 10.0.14393.8524
    • 10.0.14393.8524
    • —
    MicrosoftWindows Server 2016 (Server Core installation)
    • 10.0.14393.0 – < 10.0.14393.8524
    • 10.0.14393.8524
    MicrosoftWindows Server 2019
    • 10.0.17763.0 – < 10.0.17763.7922
    • 10.0.17763.7922
    MicrosoftWindows Server 2019 (Server Core installation)
    • 10.0.17763.0 – < 10.0.17763.7922
    • 10.0.17763.7922
    MicrosoftWindows Server 2022
    • 10.0.20348.0 – < 10.0.20348.4297
    • 10.0.20348.4297
    • 10.0.20348.4297
    • —
    MicrosoftWindows Server 2022, 23H2 Edition (Server Core installation)
    • 10.0.25398.0 – < 10.0.25398.1916
    • 10.0.25398.1916
    MicrosoftWindows Server 2025
    • 10.0.26100.0 – < 10.0.26100.6905
    • 10.0.26100.6905
    MicrosoftWindows Server 2025 (Server Core installation)
    • 10.0.26100.0 – < 10.0.26100.6905
    • 10.0.26100.6905

    Vendors and products

    Affected operating systems

    Affected operating systems
    Windowsmicrosoftwindows_server_2012r2
    Windowsmicrosoftwindows_server_2012—
    Windowsmicrosoftwindows_server_2016—
    Windowsmicrosoftwindows_server_2019—
    Windowsmicrosoftwindows_server_2022—
    Windowsmicrosoftwindows_server_2022_23h2—
    Windowsmicrosoftwindows_server_2025—

    Weakness classes (CWE)

    • CWE-502Deserialization of Untrusted Data

      Base

      The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.

      Entry at MITRE CWE-502

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited
    Reference tagged as exploitgist.github.com (opens in a new tab)PoC (publicly reported)reported, not verified—

    References & sources

    • Microsoft Security Update GuideWindows Server Update Service (WSUS) Remote Code Execution VulnerabilityVendor advisory, Patch, Vendor advisory
    • gist.github.comhawktrace/880b54fb9c07ddb028baaae401bd3951Exploit, Third-party advisory
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2025-59287government-resource, Third-party advisory, US government resource
    • bleepingcomputer.comnews/security/cisa-orders-feds-to-patch-windows-server-wsus-fla…Press coverage
    • hawktrace.comblog/CVE-2025-59287Exploit, Third-party advisory
    • vicarius.iovsociety/posts/cve-2025-59287-detection-script-rce-vulnerabilit…Third-party advisory
    • vicarius.iovsociety/posts/cve-2025-59287-mitigation-script-rce-vulnerabili…Mitigation, Third-party advisory
    • cert.atCERT.at: Angriffe gegen Microsoft WSUS Installationen - Update verfügbarcert-at
    • pwn.watchpwn.watch: Microsoft Windows: Windows Server Update Service (WSUS) Deserialization of Untrusted Data Vulnerabilitypwn-watch
    • Microsoft Security Update GuideMicrosoft advisory: Microsoft Windowspwn-watch
    • NVD (NIST)NVD: CVE-2025-59287pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch
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