CVE-2017-0213: Microsoft Windows Privilege Escalation Vulnerability

CVE-2017-0213 is a privilege-escalation vulnerability in Microsoft Windows that involves the COM Aggregate Marshaler. An attacker who can already run code on a system may use a specially crafted application to gain higher privileges. This matters because elevated access lets an attacker move laterally, disable defenses, or deploy further payloads. Public reporting associates this vulnerability with known ransomware use, so unpatched systems remain a practical risk for defenders.

How it works

The flaw sits in the Windows Component Object Model (COM) Aggregate Marshaler. COM handles object communication and marshaling across process boundaries. When the Aggregate Marshaler processes certain requests incorrectly, a local attacker can abuse it to escalate privileges.

In practice, the attacker must already be able to execute a specially crafted application on the target. That application interacts with the vulnerable COM component in a way that causes the system to grant higher privileges than the attacker’s original token allows. Exact exploit mechanics and any version-specific triggers are not detailed in the supplied summary; confirm behavior and affected builds against the vendor advisory. Because the weakness is local privilege escalation, it is typically chained after an initial foothold rather than used for remote code execution by itself.

Am I affected? How to find it in your systems

The vulnerability affects Microsoft Windows. COM is a core platform component present on desktop and server editions, so inventory should cover workstations, member servers, and domain controllers that have not received the relevant security update.

• Build a Windows inventory with asset-management or endpoint-management tools; record OS edition, build, and patch level.
• Compare installed updates against the Microsoft security update that addresses CVE-2017-0213; confirm exact KB numbers and supported versions in the vendor advisory.
• Look for systems that still allow unprivileged users to run arbitrary applications, especially shared or multi-user hosts.
• Telemetry signs of exploitation are general for this class: unexpected process creation by low-privilege users, sudden token elevation, unusual COM activation or marshaling activity, and subsequent ransomware indicators (encryption processes, shadow-copy deletion, mass file renames). Correlate with EDR, Sysmon, or Windows security event logs. Specific detection signatures must be validated against current vendor and community guidance.

How to remediate

Patch first. Apply the Microsoft updates that remediate CVE-2017-0213 exactly as directed in the vendor advisory and the CISA-required action to apply updates per vendor instructions. Use your standard patch-deployment process (WSUS, ConfigMgr, Intune, or equivalent), verify installation, and reboot where required.

• After patching, confirm the update is present via build/KB inventory and spot-check a sample of systems.
• Harden residual risk for the privilege-escalation class: enforce least privilege, remove local admin rights from standard users, enable and monitor Windows Defender Application Control or AppLocker where feasible, and keep endpoint detection and response agents current.
• Review COM-related attack surface only to the extent supported by Microsoft guidance; do not disable core COM functionality without testing, as it can break legitimate applications.

If you can't patch immediately

Reduce the chance that an attacker can reach and abuse the vulnerable component until the update can be installed.

• Segment high-value systems and restrict interactive logon and lateral movement paths so that a compromised low-privilege account cannot easily reach unpatched hosts.
• Limit which users and processes may launch arbitrary applications; application allow-listing is especially useful against local privilege-escalation chains.
• Increase monitoring for elevation events, unusual COM activity, and ransomware behaviors; alert and isolate on suspicious patterns.
• Virtual patching via host-based controls or EDR behavioral blocks may help if your vendor supplies relevant rules; treat these as temporary and still schedule the official update.
• Disable or restrict any non-essential features only if Microsoft documentation explicitly supports doing so for this issue; otherwise prefer isolation and monitoring.

If your data may have been exposed

Actively exploited privilege-escalation vulnerabilities are frequently used to deepen access after an initial breach and have been linked to ransomware. If you suspect compromise, isolate affected hosts, preserve forensic evidence, rotate credentials, and follow your incident-response plan. You can also run a free exposure scan of your email addresses against known breach data to see whether credentials or personal information have appeared in prior incidents and take appropriate follow-up steps.