CriticalCVE-2025-33073

    Windows SMB Client Elevation of Privilege Vulnerability (CVE-2025-33073)

    Published In CISA KEV since Sources: pwn.watch, CVE.org, Msrc Update Guide

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    What is affected, what to do

    A privilege escalation vulnerability in the Microsoft Windows SMB Client allows an authorized attacker to elevate privileges over a network. An attacker can execute a specially crafted malicious script to coerce the victim machine to connect back to the attacker's system using SMB and authenticate. This vulnerability is actively exploited, as evidenced by its inclusion in the CISA KEV catalog. Affected products include various versions of Windows 10, such as 1507, 1607, 1809, 21H2, and 22H2. It is imperative to apply patches as soon as they become available to mitigate this security risk.

    The vulnerability is being actively exploited; treat it as a priority. Update Microsoft Windows 10 Version 1507 to version 10.0.10240.21034, Microsoft Windows 10 Version 1607 to version 10.0.14393.8148, Microsoft Windows 10 Version 1809 to version 10.0.17763.7434. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Microsoft Windows 10 Version 1507 lt 10.0.10240.0..10.0.10240.21034
    • Microsoft Windows 10 Version 1607 lt 10.0.14393.0..10.0.14393.8148
    • Microsoft Windows 10 Version 1809 lt 10.0.17763.0..10.0.17763.7434
    • Microsoft Windows 10 Version 21H2 lt 10.0.19044.0..10.0.19044.5965
    • Microsoft Windows 10 Version 22H2 lt 10.0.19045.0..10.0.19045.5965
    • Microsoft Windows 11 version 22H2 lt 10.0.22621.0..10.0.22621.5472
    • Microsoft Windows 11 version 22H3 lt 10.0.22631.0..10.0.22631.5472
    • Microsoft Windows 11 Version 23H2 lt 10.0.22631.0..10.0.22631.5472
    • Microsoft Windows 11 Version 24H2 lt 10.0.26100.0..10.0.26100.4349
    • Microsoft Windows Server 2008 R2 Service Pack 1 lt 6.1.7601.0..6.1.7601.27769
    • Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation) lt 6.1.7601.0..6.1.7601.27769
    • Microsoft Windows Server 2008 Service Pack 2 lt 6.0.6003.0..6.0.6003.23351
    • Microsoft Windows Server 2008 Service Pack 2 (Server Core installation) lt 6.0.6003.0..6.0.6003.23351
    • Microsoft Windows Server 2012 lt 6.2.9200.0..6.2.9200.25522
    • Microsoft Windows Server 2012 (Server Core installation) lt 6.2.9200.0..6.2.9200.25522
    • Microsoft Windows Server 2012 R2 lt 6.3.9600.0..6.3.9600.22620
    • Microsoft Windows Server 2012 R2 (Server Core installation) lt 6.3.9600.0..6.3.9600.22620
    • Microsoft Windows Server 2016 lt 10.0.14393.0..10.0.14393.8148
    • Microsoft Windows Server 2016 (Server Core installation) lt 10.0.14393.0..10.0.14393.8148
    • Microsoft Windows Server 2019 lt 10.0.17763.0..10.0.17763.7434
    • Microsoft Windows Server 2019 (Server Core installation) lt 10.0.17763.0..10.0.17763.7434
    • Microsoft Windows Server 2022 lt 10.0.20348.0..10.0.20348.3807
    • Microsoft Windows Server 2022, 23H2 Edition (Server Core installation) lt 10.0.25398.0..10.0.25398.1665
    • Microsoft Windows Server 2025 lt 10.0.26100.0..10.0.26100.4349
    • Microsoft Windows Server 2025 (Server Core installation) lt 10.0.26100.0..10.0.26100.4349
    Fixed in
    • Microsoft Windows 10 Version 1507 10.0.10240.21034
    • Microsoft Windows 10 Version 1607 10.0.14393.8148
    • Microsoft Windows 10 Version 1809 10.0.17763.7434
    • Microsoft Windows 10 Version 21H2 10.0.19044.5965
    • Microsoft Windows 10 Version 22H2 10.0.19045.5965
    • Microsoft Windows 11 version 22H2 10.0.22621.5472
    • Microsoft Windows 11 version 22H3 10.0.22631.5472
    • Microsoft Windows 11 Version 23H2 10.0.22631.5472
    • Microsoft Windows 11 Version 24H2 10.0.26100.4349
    • Microsoft Windows Server 2008 R2 Service Pack 1 6.1.7601.27769
    • Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation) 6.1.7601.27769
    • Microsoft Windows Server 2008 Service Pack 2 6.0.6003.23351
    • Microsoft Windows Server 2008 Service Pack 2 (Server Core installation) 6.0.6003.23351
    • Microsoft Windows Server 2012 6.2.9200.25522
    • Microsoft Windows Server 2012 (Server Core installation) 6.2.9200.25522
    • Microsoft Windows Server 2012 R2 6.3.9600.22620
    • Microsoft Windows Server 2012 R2 (Server Core installation) 6.3.9600.22620
    • Microsoft Windows Server 2016 10.0.14393.8148
    • Microsoft Windows Server 2016 (Server Core installation) 10.0.14393.8148
    • Microsoft Windows Server 2019 10.0.17763.7434
    • Microsoft Windows Server 2019 (Server Core installation) 10.0.17763.7434
    • Microsoft Windows Server 2022 10.0.20348.3807
    • Microsoft Windows Server 2022, 23H2 Edition (Server Core installation) 10.0.25398.1665
    • Microsoft Windows Server 2025 10.0.26100.4349
    • Microsoft Windows Server 2025 (Server Core installation) 10.0.26100.4349

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

    Metrics

    8.8

    Priority

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

    Source: NVD, CVSS v3

    8.8

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: pwn.watch, CVE.org, Msrc Update Guide

    82.7 %

    EPSS score

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

    Source: FIRST EPSS, percentile 99.67

    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
    232.74 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
    8.8 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
    8.8
    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
    82.7 %
    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
    99.67
    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 · not automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 21 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-284

    Response and mitigation

    Why act now?

    Prioritisation rationale

    Any authenticated domain user can gain SYSTEM over the network, with no user interaction, on any reachable Windows host that does not enforce SMB signing — a near-perfect lateral-movement primitive once an attacker has a foothold via phishing or stolen credentials. The technique is publicly documented, reproducible with off-the-shelf tooling (plant a DNS record, coerce, relay), and its exploitation likelihood ranks among the very highest of all tracked CVEs. Exposure is greatest in AD estates with default ADIDNS permissions and unsigned SMB on servers; because a domain account is a prerequisite, treat it as a critical inside-out flaw rather than a perimeter one. For NIS2/KRITIS organisations, handle it as P1 within your critical-vulnerability SLA, DCs and Tier-0 first — the absence of a CISA ransomware flag is no reason to relax, as this class of privilege escalation is a staple of pre-ransomware intrusion phases.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Deploy the patch: Roll out Microsoft's cumulative security update (June 2025 or later) to all Windows clients and servers. Minimum fixed builds per advisory: Windows 10 1507 → 10.0.10240.21034, 1607 → 10.0.14393.8148, 1809 → 10.0.17763.7434, 21H2/22H2 → 10.0.19044.5965 / 10.0.19045.5965, Windows 11 22H2/23H2 → 10.0.22621.5472 / 10.0.22631.5472. Look up the per-build KB numbers in the vendor advisory. Patch Server editions sharing these kernel builds (e.g. 14393, 17763) and verify against the advisory.
      • Measure compliance: Use Intune/SCCM/WSUS or a PowerShell build inventory to list every host below the fixed build. Domain controllers, Tier-0 servers and file servers first.
      • Enforce SMB signing where patching lags: GPO "Microsoft network server: Digitally sign communications (always)" = Enabled (HKLM\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters\RequireSecuritySignature=1). This breaks the reflected NTLM/Kerberos relay back to the victim.
      • Sweep ADIDNS: Search AD-integrated DNS for records containing the marshalled suffix 1UWhRCAAAAAAAAAAAAAAAAAAAAAAAAAAAAwbEAYBAAAA; preserve evidence, then delete.
      • Block SMB egress: Deny outbound TCP 445/139 at the perimeter; internally allow SMB only to sanctioned file servers.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Block workstation-to-workstation SMB (TCP 445) via Windows Firewall GPO or microsegmentation. Clients normally only need SMB to file servers and DCs.
      • Configuration hardening: Require SMB signing on both server and client side (default on Windows 11 24H2 and Server 2025). Also enable LDAP signing, LDAP channel binding and Extended Protection for Authentication (EPA) on AD CS web enrollment and IIS to remove alternative relay targets.
      • Close coercion paths: Apply RPC filters (netsh rpc filter) for MS-EFSR (UUIDs c681d488-d850-11d0-8c52-00c04fd90f7e, df1941c5-fe89-4e79-bf10-463657acf44d) and MS-DFSNM; disable the Print Spooler on DCs and non-print servers; disable the WebClient service on endpoints.
      • IAM/least privilege: Remove "Authenticated Users – Create all child objects" from the DNS zone (DC=<zone>,CN=MicrosoftDNS,DC=DomainDnsZones) and restrict to DNS admins/the DHCP service account, so low-privileged accounts cannot plant attacker DNS records.
      • NTLM reduction: Enable NTLM auditing ("Network security: Restrict NTLM: Audit incoming NTLM traffic") and progressively restrict; place privileged accounts in Protected Users.

    3. Runbook step 3

      Detection rules

      • Reflected logon (Security log, Event ID 4624): LogonType 3, TargetUserName equals the host's own machine account (<HOST>$), IpAddress not local. KQL: SecurityEvent | where EventID==4624 and LogonType==3 and TargetUserName==strcat(Computer_short,"$") and IpAddress !in ("127.0.0.1","::1","-")
      • Malicious DNS records (DC, Event ID 5136/5137 with DS auditing): New dnsNode objects whose name contains 1UWhRCAAAAAAAAAAAAAAAAAAAAAAAAAAAAwbEAYBAAAA. Sigma shape: EventID: 5137 | ObjectDN|contains: '1UWhRCAAAAAAAAAAAAAAAAAAAAAAAAAAAAwbEAYBAAAA'. Cross-check DNS debug logs/Zeek dns.log for queries matching the pattern.
      • Coercion attempts (Event ID 5145, Detailed File Share): IPC$ access with RelativeTargetName in (efsrpc, lsarpc, netdfs, spoolss) originating from workstation IPs. Zeek dce_rpc.log: EfsRpcOpenFileRaw, EfsRpcEncryptFileSrv, NetrDfsAddStdRoot, RpcRemoteFindFirstPrinterChangeNotificationEx.
      • Post-exploitation (Sysmon EID 1 / EDR): SYSTEM processes spawned by services.exe shortly after a 4624 logon of the host's own machine account (remote service creation, cf. Event ID 7045); access to HKLM\SAM/SECURITY hives (Sysmon EID 12/13).
      • Network (Suricata/Zeek): Outbound SMB from a server to a workstation IP immediately followed by inbound SMB from that same peer — the characteristic reflection pattern.

    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

    Improper access control in Windows SMB allows an authorized attacker to elevate privileges over a network.

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

    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 10 Version 1507
    • 10.0.10240.0 – < 10.0.10240.21034
    • 10.0.10240.21034
    MicrosoftWindows 10 Version 1607
    • 10.0.14393.0 – < 10.0.14393.8148
    • 10.0.14393.8148
    MicrosoftWindows 10 Version 1809
    • 10.0.17763.0 – < 10.0.17763.7434
    • 10.0.17763.7434
    MicrosoftWindows 10 Version 21H2
    • 10.0.19044.0 – < 10.0.19044.5965
    • 10.0.19044.5965
    MicrosoftWindows 10 Version 22H2
    • 10.0.19045.0 – < 10.0.19045.5965
    • 10.0.19045.5965
    MicrosoftWindows 11 version 22H2
    • 10.0.22621.0 – < 10.0.22621.5472
    • 10.0.22621.5472
    MicrosoftWindows 11 version 22H3
    • 10.0.22631.0 – < 10.0.22631.5472
    • 10.0.22631.5472
    MicrosoftWindows 11 Version 23H2
    • 10.0.22631.0 – < 10.0.22631.5472
    • 10.0.22631.5472
    MicrosoftWindows 11 Version 24H2
    • 10.0.26100.0 – < 10.0.26100.4349
    • 10.0.26100.4349
    MicrosoftWindows Server 2008 R2 Service Pack 1
    • 6.1.7601.0 – < 6.1.7601.27769
    • 6.1.7601.27769
    MicrosoftWindows Server 2008 R2 Service Pack 1 (Server Core installation)
    • 6.1.7601.0 – < 6.1.7601.27769
    • 6.1.7601.27769
    MicrosoftWindows Server 2008 Service Pack 2
    • 6.0.6003.0 – < 6.0.6003.23351
    • 6.0.6003.23351
    MicrosoftWindows Server 2008 Service Pack 2 (Server Core installation)
    • 6.0.6003.0 – < 6.0.6003.23351
    • 6.0.6003.23351
    MicrosoftWindows Server 2012
    • 6.2.9200.0 – < 6.2.9200.25522
    • 6.2.9200.25522
    MicrosoftWindows Server 2012 (Server Core installation)
    • 6.2.9200.0 – < 6.2.9200.25522
    • 6.2.9200.25522
    MicrosoftWindows Server 2012 R2
    • 6.3.9600.0 – < 6.3.9600.22620
    • 6.3.9600.22620
    MicrosoftWindows Server 2012 R2 (Server Core installation)
    • 6.3.9600.0 – < 6.3.9600.22620
    • 6.3.9600.22620
    MicrosoftWindows Server 2016
    • 10.0.14393.0 – < 10.0.14393.8148
    • 10.0.14393.8148
    MicrosoftWindows Server 2016 (Server Core installation)
    • 10.0.14393.0 – < 10.0.14393.8148
    • 10.0.14393.8148
    MicrosoftWindows Server 2019
    • 10.0.17763.0 – < 10.0.17763.7434
    • 10.0.17763.7434
    MicrosoftWindows Server 2019 (Server Core installation)
    • 10.0.17763.0 – < 10.0.17763.7434
    • 10.0.17763.7434
    MicrosoftWindows Server 2022
    • 10.0.20348.0 – < 10.0.20348.3807
    • 10.0.20348.3807
    MicrosoftWindows Server 2022, 23H2 Edition (Server Core installation)
    • 10.0.25398.0 – < 10.0.25398.1665
    • 10.0.25398.1665
    MicrosoftWindows Server 2025
    • 10.0.26100.0 – < 10.0.26100.4349
    • 10.0.26100.4349
    MicrosoftWindows Server 2025 (Server Core installation)
    • 10.0.26100.0 – < 10.0.26100.4349
    • 10.0.26100.4349

    Vendors and products

    Affected operating systems

    Affected operating systems
    Windowsmicrosoftwindows_10_1507—
    Windowsmicrosoftwindows_10_1607—
    Windowsmicrosoftwindows_10_1809—
    Windowsmicrosoftwindows_10_21h2—
    Windowsmicrosoftwindows_10_22h2—
    Windowsmicrosoftwindows_11_22h2—
    Windowsmicrosoftwindows_11_23h2—
    Windowsmicrosoftwindows_11_24h2—
    Windowsmicrosoftwindows_server_2008r2
    Windowsmicrosoftwindows_server_2008—
    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-284Improper Access Control

      Pillar

      The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.

      Entry at MITRE CWE-284

    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
    PoC-in-GitHub (nomi-sec)CVE-2025-33073 (opens in a new tab)github.comPoC (publicly reported)reported, not verified
    PoC-in-GitHub (nomi-sec)CVE-2025-33073 (opens in a new tab)github.comPoC (publicly reported)reported, not verified

    References & sources

    • Microsoft Security Update GuideWindows SMB Client Elevation of Privilege VulnerabilityVendor advisory, Patch, Vendor advisory
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2025-33073government-resource, US government resource
    • vicarius.iovsociety/posts/cve-2025-33073-detection-script-improper-access-…Third-party advisory
    • vicarius.iovsociety/posts/cve-2025-33073-mitigation-script-improper-access…Mitigation, Third-party advisory
    • pwn.watchpwn.watch: Microsoft Windows: Windows SMB Client Improper Access Control Vulnerabilitypwn-watch
    • Microsoft Security Update GuideMicrosoft advisory: Microsoft Windowspwn-watch
    • NVD (NIST)NVD: CVE-2025-33073pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch
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