CVE-2021-36955 Microsoft Windows: privilege escalation
In plain words: Something running with limited rights can promote itself to full control. Turns a small foothold (like a malicious app) into administrator or system-level access.
Confirmed exploited by CISA on · US federal patch deadline Nov 17, 2021
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 Common Log File System (CLFS) Driver Privilege Escalation Vulnerability
- Product
- Microsoft Windows
- CISA description
- Microsoft Windows Common Log File System (CLFS) driver contains an unspecified vulnerability that allows for privilege escalation.
- Type of flaw
- Privilege escalation
- Confirmed exploited
- Nov 3, 2021 — known to be used in ransomware attacks
- US federal patch deadline
- Nov 17, 2021
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Answering about CVE-2021-36955 ·
Questions about CVE-2021-36955
Is CVE-2021-36955 being exploited?
Yes. CISA added CVE-2021-36955 to its Known Exploited Vulnerabilities catalog on Nov 3, 2021, which means there is reliable evidence of real-world attacks, including by ransomware groups.
How do I fix CVE-2021-36955?
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-2021-36955?
Only if you use Microsoft Windows. Used in ransomware, which spreads to ordinary people and small businesses.