CVE-2018-8639 Microsoft Windows: software flaw
In plain words: A mistake in the software that attackers have found a way to abuse. Depends on the product — see the description and the vendor advisory.
Confirmed exploited by CISA on · US federal patch deadline Mar 24, 2025
What to do
- Install Microsoft's security update for Windows. If no update exists, follow the vendor's workaround or stop using the product until one ships.
- Turn on automatic updates for the operating system and for Office, PDF and archive apps.
- Be careful with unexpected attachments — documents, .zip/.rar files and shortcuts are common bait.
- Use a normal (non-admin) account day to day and keep built-in protection like Microsoft Defender on.
Who is affected
Could reach you. Used in ransomware, which spreads to ordinary people and small businesses.
What's at risk: Your files, saved passwords and accounts. Many of these let a program that is already running gain full administrator control.
The details
- Official name
- Microsoft Windows Win32k Improper Resource Shutdown or Release Vulnerability
- Product
- Microsoft Windows
- CISA description
- Microsoft Windows Win32k contains an improper resource shutdown or release vulnerability that allows for local, authenticated privilege escalation. An attacker who successfully exploited this vulnerability could run arbitrary code in kernel mode.
- Type of flaw
- Software flaw (CWE-404)
- Confirmed exploited
- Mar 3, 2025 — known to be used in ransomware attacks
- US federal patch deadline
- Mar 24, 2025
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Answering about CVE-2018-8639 ·
Questions about CVE-2018-8639
Is CVE-2018-8639 being exploited?
Yes. CISA added CVE-2018-8639 to its Known Exploited Vulnerabilities catalog on Mar 3, 2025, which means there is reliable evidence of real-world attacks, including by ransomware groups.
How do I fix CVE-2018-8639?
Install Microsoft's security update for Windows. If no update exists, follow the vendor's workaround or stop using the product until one ships. Turn on automatic updates for the operating system and for Office, PDF and archive apps.
Am I affected by CVE-2018-8639?
Only if you use Microsoft Windows. Used in ransomware, which spreads to ordinary people and small businesses.