CVE-2021-22555 Linux Kernel: 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 Oct 27, 2025
What to do
- Install Linux's security update for Kernel. 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
- Linux Kernel Heap Out-of-Bounds Write Vulnerability
- Product
- Linux Kernel
- CISA description
- Linux Kernel contains a heap out-of-bounds write vulnerability that could allow an attacker to gain privileges or cause a DoS (via heap memory corruption) through user name space.
- Type of flaw
- Memory-safety flaw (CWE-787)
- Confirmed exploited
- Oct 6, 2025
- US federal patch deadline
- Oct 27, 2025
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Answering about CVE-2021-22555 ·
Questions about CVE-2021-22555
Is CVE-2021-22555 being exploited?
Yes. CISA added CVE-2021-22555 to its Known Exploited Vulnerabilities catalog on Oct 6, 2025, which means there is reliable evidence of real-world attacks.
How do I fix CVE-2021-22555?
Install Linux's security update for Kernel. 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-2021-22555?
Only if you use Linux Kernel. This one is aimed at devices or apps of the kind people own.