CVE-2026-21525 Microsoft Windows: memory-safety flaw
In plain words: The program mishandles the memory it uses to keep track of data. A specially made input can scramble that memory. Usually lets an attacker crash the program or run their own code with its permissions.
Confirmed exploited by CISA on · US federal patch deadline Mar 3, 2026
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. This one is aimed at devices or apps of the kind people own.
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 NULL Pointer Dereference Vulnerability
- Product
- Microsoft Windows
- CISA description
- Microsoft Windows Remote Access Connection Manager contains a NULL pointer dereference that could allow an unauthorized attacker to deny service locally.
- Type of flaw
- Memory-safety flaw (CWE-476)
- Confirmed exploited
- Feb 10, 2026
- US federal patch deadline
- Mar 3, 2026
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Answering about CVE-2026-21525 ·
Questions about CVE-2026-21525
Is CVE-2026-21525 being exploited?
Yes. CISA added CVE-2026-21525 to its Known Exploited Vulnerabilities catalog on Feb 10, 2026, which means there is reliable evidence of real-world attacks.
How do I fix CVE-2026-21525?
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-2026-21525?
Only if you use Microsoft Windows. This one is aimed at devices or apps of the kind people own.