Microsoft Windows Graphics Device Interface (GDI) Remote Code Execution Vulnerability (CVE-2016-3393)
Published In CISA KEV since Sources: CVE.org
What is affected, what to do
Graphics Device Interface (aka GDI or GDI+) 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 allows remote attackers to execute arbitrary code via a crafted web site, aka "Windows Graphics Component RCE 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 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
68.5 %
EPSS score
High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
Source: FIRST EPSS, percentile 99.33
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- 217.93 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- 68.5 %
- 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- 99.33
- 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 GDI font-handling flaw was used as a zero-day in targeted attacks. It mainly serves as the privilege-escalation and sandbox-escape link that follows a browser exploit in a chain. The vector is local and needs user interaction, but no prior authentication, and success means full loss of confidentiality, integrity and availability. EPSS puts exploitation likelihood in the very high range, and CISA does not flag known ransomware use. Fully patched, supported Windows builds carry little residual risk. Out-of-support Windows 7, Server 2008 and early Windows 10 machines with web access, common in KRITIS, OT and manufacturing estates, should be treated as high priority for isolation or replacement.
Runbook step 1
Immediate response (0-24 h)
- Scope affected assets: Query CMDB, SCCM/Intune or EDR inventory for Windows Vista SP2, Windows 7 SP1, Windows 8.1/RT 8.1, Windows 10 1507/1511/1607, Windows Server 2008 SP2/R2 SP1 and Server 2012/2012 R2. Most of these are past end of support. Treat any host lacking current cumulative updates as vulnerable.
- Deploy the security update: A patch is available from the vendor — look up the per-OS KB number for CVE-2016-3393 in the Microsoft Security Update Guide. On supported systems the current cumulative update or Monthly Rollup normally supersedes it. Verify installation via
Get-HotFixor an EDR query. - Isolate unpatchable legacy hosts: Cut direct internet access for systems that cannot be updated (e.g. Windows 7 without ESU in OT or lab networks). Prohibit web browsing and email clients on them.
- Stop browsing from servers: Use GPO and proxy policy to block outbound HTTP(S) from interactive sessions on Windows Server 2008/2012. The delivery vector is a crafted website.
- Strip local admin rights: The flaw is typically used for privilege escalation after browser compromise. Standard-user accounts limit what the first stage of the chain can achieve.
Runbook step 2
Mitigation layers
- Network / proxy: Block font downloads (
.ttf,.otf,.woff,.eot,font/*MIME types) from uncategorised or newly registered domains at the secure web gateway. Force legacy VLANs through a categorising proxy with TLS inspection. - Endpoint hardening (Windows 10): Enable "Untrusted Font Blocking" via GPO (Computer Configuration → Administrative Templates → System → Mitigation Options → "Block untrusted fonts and log events"). This prevents fonts from loading outside
%windir%\Fonts. - Exploit protection: Via Windows Defender Exploit Guard, or EMET on legacy systems, enforce "Disable Win32k system calls" (where compatible), ASLR and DEP for browser processes (
iexplore.exe,chrome.exe,firefox.exe,msedge.exe). - Application control: Use AppLocker or WDAC to deny execution from
%TEMP%,%APPDATA%and browser cache paths. This breaks the payload-staging step after code execution. - Browser isolation: Put high-risk groups (admins, developers, OT engineers) behind remote browser isolation or Application Guard. Alternatively, provide dedicated unprivileged browsing VMs.
- IAM: Enforce admin tiering and deny web access for privileged accounts through a proxy rule keyed on the AD group.
- Network / proxy: Block font downloads (
Runbook step 3
Detection rules
- Sysmon EID 1 / Security 4688 — suspicious ancestry: A browser spawns a shell or LOLBin. KQL:
DeviceProcessEvents | where InitiatingProcessFileName in~ ("iexplore.exe","chrome.exe","firefox.exe","msedge.exe") and FileName in~ ("cmd.exe","powershell.exe","rundll32.exe","regsvr32.exe","mshta.exe") - Privilege escalation: A browser child process runs at
Systemintegrity or asNT AUTHORITY\SYSTEM. A suitable Sigma shape isParentImage|endswith: browserANDIntegrityLevel: System. Correlate with Security 4672 in an unexpected user context. - Crash artefacts: Look for Application log Event ID 1000/1001 (WER) with faulting module
win32k.sys,gdi32.dll,gdiplus.dllorfontdrvhost.exe. Also check for BugChecks (System Event ID 1001) referencing win32k. Failed exploitation attempts often leave these traces. - Fonts outside standard paths: Sysmon EID 11 where
TargetFilenameends in.ttf/.otf/.fonunder\Temp\,\INetCache\or\AppData\. On Windows 10, also monitorMicrosoft-Windows-Win32k/OperationalEvent ID 260 (untrusted font blocked). - Network telemetry (Zeek/Suricata): Hunt
http.log/files.logformime_typeapplication/font-*/font/*served by rare domains. Correlate with the same host connecting to new external IPs within minutes.
- Sysmon EID 1 / Security 4688 — suspicious ancestry: A browser spawns a shell or LOLBin. KQL:
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
Graphics Device Interface (aka GDI or GDI+) 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 allows remote attackers to execute arbitrary code via a crafted web site, aka "Windows Graphics Component RCE Vulnerability."
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 |
References & sources
- securitytracker.com1036988Vulnerability database, x_refsource_SECTRACK, Broken link, Third-party advisory, Vulnerability database
- securityfocus.com93377Vulnerability database, x_refsource_BID, Broken link, Third-party advisory, Vulnerability database
- docs.microsoft.comMS16-120Vendor advisory, x_refsource_MS, Patch, Vendor advisory
- cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2016-3393government-resource, US government resource
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<a href="https://intel.neosec.eu/en/cve/CVE-2016-3393"><img src="https://intel.neosec.eu/badge/cve/CVE-2016-3393.svg?lang=en" alt="CVE-2016-3393 – NEOSEC Intel" height="20"></a>