Microsoft Windows Kernel Privilege Escalation Vulnerability (CVE-2016-3309)
Published In CISA KEV since Sources: CVE.org
What is affected, what to do
The kernel-mode drivers in Microsoft Windows Vista SP2; Windows Server 2008 SP2 and R2 SP1; Windows 7 SP1; Windows 8.1; Windows Server 2012 Gold and R2; Windows RT 8.1; and Windows 10 Gold, 1511, and 1607 allow local users to gain privileges via a crafted application, aka "Win32k Elevation of Privilege Vulnerability," a different vulnerability than CVE-2016-3308, CVE-2016-3310, and CVE-2016-3311.
The vulnerability is being actively exploited; treat it as a priority. CISA lists it as used in ransomware campaigns. 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 Server 2008
eq r2..r2 - Microsoft Windows Server 2012
eq r2..r2
- Microsoft Windows Server 2008
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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
20.5 %
EPSS score
Elevated — model estimates 10-50% exploitation likelihood.
Source: FIRST EPSS, percentile 97.5
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- 240.07 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- 20.5 %
- 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- 97.5
- 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
Response and mitigation
Why act now?
Prioritisation rationale
This flaw requires low-privileged local access, but it then reliably delivers kernel-mode code execution. That makes it a staple post-initial-access step in intrusion chains, and CISA explicitly flags known use in ransomware campaigns. Exploitation likelihood is very high, and public exploits have circulated for years. Today's realistic exposure is concentrated in neglected legacy assets: OT-adjacent HMI workstations, line-of-business servers on Server 2008/2012, and frozen Windows 10 LTSB 1607 builds, all common in KRITIS environments. On a fully patched fleet the risk is low, but any unpatched legacy host that users can reach should be treated as high priority, because it hands attackers a direct path to SYSTEM and to encryption.
Runbook step 1
Immediate response (0-24 h)
- Inventory exposed hosts: Use SCCM/Intune, WSUS reports or EDR inventory to find every Windows Vista SP2, Server 2008 SP2/R2 SP1, Windows 7 SP1, 8.1/RT 8.1, Server 2012/2012 R2 and Windows 10 Gold/1511/1607 host. Treat any host lacking cumulative updates or security rollups from August 2016 onward as vulnerable.
- Apply the vendor fix: A patch for this Win32k flaw is available from Microsoft. Look up the bulletin and KB ID in the vendor advisory. On supported builds, the current cumulative update already includes the fix. Verify with
Get-HotFixor the OS build number. - Isolate unsupported systems: Vista, Windows 7 and Server 2008 without ESU, as well as Windows 10 1507/1511/1607, receive no further updates. Move them to a dedicated VLAN and restrict interactive logon and RDP (TCP 3389) to whitelisted jump hosts. Schedule their replacement.
- Hunt on exposed legacy hosts: This bug is used after initial access (phishing, RDP, webshells). On unpatched hosts with user access, look for SYSTEM processes with user-level parents (see Detection rules).
- Rotate credentials if compromise is suspected: Reset local admin passwords (LAPS), service accounts and cached domain credentials on affected hosts. Gaining SYSTEM enables LSASS dumping.
Runbook step 2
Mitigation layers
- Application control (endpoint): Use WDAC or AppLocker to block unsigned or unapproved binaries from user-writable paths:
%TEMP%,%APPDATA%,%LOCALAPPDATA%,C:\Users\PublicandDownloads. The exploit requires a crafted application to run locally. - Least privilege (IAM): Restrict
Allow log on locallyandAllow log on through Remote Desktop Servicesvia GPO so only admin groups can log on to servers. Standard users should never get sessions on servers. Shared terminal servers running legacy OS versions should be patched or retired first. - Network segmentation: Place unpatchable legacy hosts in a quarantine zone. Block SMB (TCP 445), RDP (TCP 3389) and WinRM (TCP 5985/5986) outbound from that zone so a local privilege escalation cannot become a lateral-movement pivot.
- Post-exploitation hardening: Enable LSA protection (
RunAsPPL=1) and Credential Guard where supported. On Defender estates, enable the ASR rule "Block credential stealing from LSASS". This does not stop the exploit, but it limits the blast radius once SYSTEM is obtained. - Initial-access controls: Block executable attachments (
.exe,.scr,.js,.hta) at the mail gateway and disable internet-sourced Office macros via GPO. This cuts off the delivery path that precedes the exploit.
- Application control (endpoint): Use WDAC or AppLocker to block unsigned or unapproved binaries from user-writable paths:
Runbook step 3
Detection rules
- Integrity-level jump (EDR/MDE):
DeviceProcessEvents | where ProcessIntegrityLevel == "System" and InitiatingProcessIntegrityLevel in ("Medium","Low") and InitiatingProcessFileName !in~ ("consent.exe","msiexec.exe")— this is the core signal for a successful kernel privilege escalation. - Sysmon EID 1 / Security 4688: Alert on
cmd.exe,powershell.exeorwhoami.exerunning asNT AUTHORITY\SYSTEMwhoseParentImagesits in a user path (\Users\,\AppData\,\Temp\). Sigma shape:selection: User|contains: 'SYSTEM' AND ParentImage|contains: ['\AppData\','\Temp\','\Users\Public\']. - Kernel crashes from failed attempts: Watch System Event ID 1001 (BugCheck) and WER entries naming
win32k.sysas the faulting module. Clusters of blue screens on legacy hosts can indicate unstable exploit attempts. - Dropped binary followed by a SYSTEM shell: Correlate Sysmon EID 11 (FileCreate) of an
.exein%TEMP%, then EID 1 of that file within minutes, then a SYSTEM child process. SPL:index=sysmon EventCode=1 User="NT AUTHORITY\\SYSTEM" ParentImage="*\\AppData\\*". - Follow-on activity: Watch for Security 4720/4732 (account created or added to Administrators),
lsass.exeaccess (Sysmon EID 10 withGrantedAccess 0x1010/0x1410) andvssadmin delete shadows. The last is a classic ransomware precursor after privileges have been escalated.
- Integrity-level jump (EDR/MDE):
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 Vista SP2; Windows Server 2008 SP2 and R2 SP1; Windows 7 SP1; Windows 8.1; Windows Server 2012 Gold and R2; Windows RT 8.1; and Windows 10 Gold, 1511, and 1607 allow local users to gain privileges via a crafted application, aka "Win32k Elevation of Privilege Vulnerability," a different vulnerability than CVE-2016-3308, CVE-2016-3310, and CVE-2016-3311.
Source: NVD (NIST), cvelistv5, CISA KEV Catalog, CVE.org (MITRE)
Vendors and products
- Microsoft Windows 10 1507
- Microsoft Windows 10 1511
- Microsoft Microsoft Windows 10 1607
- 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 Vista Gold on X64
Affected operating systems
| Windows | microsoft | windows_10_1507 | — |
| Windows | microsoft | windows_10_1511 | — |
| Windows | microsoft | windows_10_1607 | — |
| 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_vista | — |
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 42960 (opens in a new tab)exploit-db.com | PoC (publicly reported)reported, not verified | — |
References & sources
- docs.microsoft.comMS16-098Vendor advisory, x_refsource_MS, Patch, Vendor advisory
- exploit-db.com42960Exploit, x_refsource_EXPLOIT-DB, Broken link, Third-party advisory, Vulnerability database
- securitytracker.com1036572Vulnerability database, x_refsource_SECTRACK, Broken link, Third-party advisory, Vulnerability database
- securityfocus.com92297Vulnerability database, x_refsource_BID, Broken link, Third-party advisory, Vulnerability database
- cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2016-3309government-resource, US government resource
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<a href="https://intel.neosec.eu/en/cve/CVE-2016-3309"><img src="https://intel.neosec.eu/badge/cve/CVE-2016-3309.svg?lang=en" alt="CVE-2016-3309 – NEOSEC Intel" height="20"></a>