Microsoft Win32k Privilege Escalation Vulnerability (CVE-2017-0263)
Published In CISA KEV since Sources: CVE.org
What is affected, what to do
The kernel-mode drivers in Microsoft Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8.1, Windows Server 2012 Gold and R2, Windows RT 8.1, Windows 10 Gold, 1511, 1607, 1703, and Windows Server 2016 allow local users to gain privileges via a crafted application, aka "Win32k Elevation of Privilege Vulnerability."
The vulnerability is being actively exploited; treat it as a priority. The available sources name no fixed version. Check the vendor guidance in the references below. Immediate actions, mitigation and detection rules are in the runbook below.
- Affected
- Microsoft Windows
eq Microsoft Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8.1, Windows Server 2012 Gold and R2, Windows RT 8.1, Windo..Microsoft Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8.1, Windows Server 2012 Gold and R2, Windows RT 8.1, Windo
- Microsoft Windows
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Metrics
7.8
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: NVD, CVSS v3
7.8
CVSS v3
Severity High on the scale from 0 to 10.
Source: CVE.org
10.0 %
EPSS score
Elevated — model estimates 10-50% exploitation likelihood.
Source: FIRST EPSS, percentile 95.6
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- 212.11 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 exploited
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- 7.8 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- 7.8
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- 10.0 %
- Elevated — model estimates 10-50% exploitation likelihood.
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- 95.6
- 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 10 February 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-416
Response and mitigation
Why act now?
Prioritisation rationale
This flaw lets a low-privileged local user take full control of the system with no further user interaction. Attackers use it as a second stage after initial access, typically chained with weaponised Office documents in targeted spear-phishing, to break out of a restricted session into SYSTEM. Exploitation likelihood is high, and CISA records no known ransomware use. Priority is low for fully patched Windows 10/11 and Server 2016+ estates. It is high for organisations still running EOL builds, especially terminal servers or OT-adjacent workstations, which often have not received patches since 2017.
Runbook step 1
Immediate response (0-24 h)
- Verify patch level and deploy the fix: Microsoft fixed this vulnerability in its May 2017 security updates (Patch Tuesday). Look up the KB number for each OS version in the Microsoft Security Update Guide entry for CVE-2017-0263. Any later cumulative update or Monthly Rollup includes the fix.
- Hunt down legacy builds: Affected versions are Windows 7 SP1, Server 2008 SP2/R2 SP1, Windows 8.1/RT 8.1, Server 2012/2012 R2 and Windows 10 1507/1511/1607/1703, most of which are end-of-life. Query your CMDB or EDR inventory for these builds. Flag any host without patches from May 2017 onward as critical.
- Patch multi-user hosts first: Prioritise terminal servers (RDS/Citrix), jump hosts and shared workstations. On these systems, any logged-on user can escalate to SYSTEM.
- If compromise is suspected: Isolate the host via EDR network containment. Rotate local admin and service account passwords (enforce LAPS). Treat any domain credentials cached on the host as compromised.
- Close the initial-access path: Exploitation requires local code execution. Block macros and active content in Office files from the internet (GPO "Block macros from running in Office files from the Internet"). Bring legacy Office installs up to date.
Runbook step 2
Mitigation layers
- Endpoint hardening: Use WDAC or AppLocker to block execution from user-writable paths (
%TEMP%,%APPDATA%,Downloads). Without a dropped exploit binary, the escalation cannot run. - Attack Surface Reduction: Enable the ASR rules "Block Office applications from creating child processes" and "Block Office applications from injecting code into other processes". Pairing an Office exploit with a Win32k privilege escalation is a documented pattern.
- Network segmentation for EOL systems: Move unpatchable legacy hosts (common in OT/KRITIS environments) into a dedicated VLAN. Deny outbound internet access and block SMB/RDP towards server and client segments. This limits lateral movement after a successful escalation.
- Least privilege / IAM: Restrict interactive logons on servers to accounts that need them ("Allow log on locally" / "Allow log on through Remote Desktop Services"). Enforce admin tiering so that a local SYSTEM compromise does not immediately expose Domain Admin credentials.
- Credential Guard / LSA protection: Enable
RunAsPPLand Credential Guard where supported. This makes it harder to turn SYSTEM rights into LSASS credential dumping.
- Endpoint hardening: Use WDAC or AppLocker to block execution from user-writable paths (
Runbook step 3
Detection rules
- Sysmon EID 1 / Security EID 4688: Look for processes running at
IntegrityLevel=Systemwith aMediumparent that is notservices.exe,wininit.exeorsvchost.exe. KQL:DeviceProcessEvents | where ProcessIntegrityLevel == "System" and InitiatingProcessIntegrityLevel == "Medium" and InitiatingProcessFileName !in~ ("services.exe","svchost.exe","wininit.exe") - Office process ancestry: Look for
winword.exe,excel.exeorpowerpnt.exeas an ancestor of any process running asNT AUTHORITY\SYSTEM. Sigma shape:ParentImage|endswith: '\WINWORD.EXE'withUser|contains: 'SYSTEM'. - EDR kernel telemetry: Review alerts for token manipulation or token stealing (process token swapped for the SYSTEM token). Also review anomalous Win32k syscall activity from unsigned binaries in user paths.
- Post-escalation activity: Watch for Security EID 4720/4732 (new local account, addition to Administrators), EID 7045 (new service) and Sysmon EID 10 targeting
lsass.exe. These are most suspicious shortly after a standard user runs an unknown binary. - Crash artefacts: System EID 1001 (BugCheck) or BSODs referencing
win32k.syson unpatched hosts can point to failed exploit attempts.
- Sysmon EID 1 / Security EID 4688: Look for processes running at
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
The kernel-mode drivers in Microsoft Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8.1, Windows Server 2012 Gold and R2, Windows RT 8.1, Windows 10 Gold, 1511, 1607, 1703, and Windows Server 2016 allow local users to gain privileges via a crafted application, aka "Win32k Elevation of Privilege Vulnerability."
Source: NVD (NIST), 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 versions | Fixed in | ||
|---|---|---|---|
| Microsoft Corporation | Microsoft Windows |
|
|
Vendors and products
- Microsoft Windows 10 1507
- Microsoft Windows 10 1511
- Microsoft Microsoft Windows 10 1607
- Microsoft Windows 10 1703
- Microsoft Microsoft Windows 7
- Microsoft Microsoft Windows 8.1
- Microsoft Microsoft Windows RT 8.1
- Microsoft Microsoft Windows Server 2008
- Microsoft Microsoft Windows Server 2012
- Microsoft Microsoft Windows Server 2016
- Microsoft Corporation Microsoft Windows
Affected operating systems
| Windows | microsoft | windows_10_1507 | — |
| Windows | microsoft | windows_10_1511 | — |
| Windows | microsoft | windows_10_1607 | — |
| Windows | microsoft | windows_10_1703 | — |
| Windows | microsoft | windows_7 | — |
| Windows | microsoft | windows_8.1 | — |
| Windows | microsoft | windows_rt_8.1 | — |
| Windows | microsoft | windows_server_2008 | r2 |
| Windows | microsoft | windows_server_2008 | — |
| Windows | microsoft | windows_server_2012 | r2 |
| Windows | microsoft | windows_server_2012 | — |
| Windows | microsoft | windows_server_2016 | — |
Weakness classes (CWE)
CWE-416Use After Free
Variant
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
Entry at MITRE CWE-416
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.
| CISA KEV Catalog | CISA Known Exploited Vulnerability (opens in a new tab)cisa.gov | actively exploited | |
| Exploit-DB | EDB-ID 44478 (opens in a new tab)exploit-db.com | PoC (publicly reported)reported, not verified | — |
References & sources
- portal.msrc.microsoft.comen-US/security-guidance/advisory/CVE-2017-0263x_refsource_CONFIRM, Patch, Vendor advisory
- securitytracker.com1038449Vulnerability database, x_refsource_SECTRACK, Broken link, Third-party advisory, Vulnerability database
- securityfocus.com98258Vulnerability database, x_refsource_BID, Broken link, Third-party advisory, Vulnerability database
- xiaodaozhi.comexploit/117.htmlx_refsource_MISC, Exploit, Third-party advisory
- exploit-db.com44478Exploit, x_refsource_EXPLOIT-DB, Exploit, Third-party advisory, Vulnerability database
- cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2017-0263government-resource, US government resource
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<a href="https://intel.neosec.eu/en/cve/CVE-2017-0263"><img src="https://intel.neosec.eu/badge/cve/CVE-2017-0263.svg?lang=en" alt="CVE-2017-0263 – NEOSEC Intel" height="20"></a>