CVE-2025-21661
📋 TL;DR
A memory leak vulnerability in the Linux kernel's GPIO virtuser driver prevents proper cleanup of lookup tables when device creation fails. This causes resource exhaustion over time and blocks subsequent device creation attempts. Systems using GPIO virtuser devices via configfs are affected.
💻 Affected Systems
- Linux kernel
📦 What is this software?
Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →⚠️ Risk & Real-World Impact
Worst Case
Kernel memory exhaustion leading to system instability, crashes, or denial of service preventing GPIO virtuser device creation.
Likely Case
Gradual memory leak causing performance degradation over time and inability to create GPIO virtuser devices after failed attempts.
If Mitigated
Minimal impact with proper monitoring and memory limits in place.
🎯 Exploit Status
Requires local access and ability to create/configure GPIO virtuser devices. Exploitation leads to resource exhaustion rather than privilege escalation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions containing commits a619cba8c69c434258ff4101d463322cd63e1bdc and d72d0126b1f6981f6ce8b4247305f359958c11b5
Vendor Advisory: https://git.kernel.org/stable/c/a619cba8c69c434258ff4101d463322cd63e1bdc
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version from your distribution vendor. 2. Reboot system to load new kernel. 3. Verify gpio-virtuser driver is not leaking memory with kmemleak monitoring.
🔧 Temporary Workarounds
Disable gpio-virtuser module
linuxPrevent loading of vulnerable driver if not needed
echo 'blacklist gpio_virtuser' > /etc/modprobe.d/blacklist-gpio-virtuser.conf
rmmod gpio_virtuser
Restrict configfs access
linuxLimit who can create GPIO virtuser devices
chmod 750 /sys/kernel/config/gpio-virtuser
setfacl -m u:root:rwx,g:gpio:rx,o:- /sys/kernel/config/gpio-virtuser
🧯 If You Can't Patch
- Monitor kernel memory usage and restart system if leaks are detected
- Disable GPIO virtuser functionality if not required for system operation
🔍 How to Verify
Check if Vulnerable:
Check if gpio-virtuser module is loaded: lsmod | grep gpio_virtuser. Check kernel version: uname -r and compare with patched versions.Check Version:
uname -rVerify Fix Applied:
After patching, test GPIO virtuser device creation via configfs and monitor for memory leaks with kmemleak.📡 Detection & Monitoring
Log Indicators:
- Kernel oom-killer messages
- Memory allocation failures in dmesg
- GPIO virtuser probe failure messages
Network Indicators:
- None - local vulnerability only
SIEM Query:
source="kernel" AND ("gpio_virtuser" OR "out of memory" OR "kmemleak")