CVE-2025-21739
📋 TL;DR
A use-after-free vulnerability in the Linux kernel's UFS (Universal Flash Storage) driver allows attackers to potentially crash the system or execute arbitrary code. This affects Linux systems using UFS storage devices. The vulnerability occurs during driver initialization errors or removal when crypto cleanup code accesses already freed memory.
💻 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 →⚠️ Risk & Real-World Impact
Worst Case
Kernel panic leading to system crash or potential arbitrary code execution with kernel privileges, resulting in complete system compromise.
Likely Case
System instability, kernel crashes, or denial of service affecting storage operations on UFS devices.
If Mitigated
Limited impact if systems don't use UFS storage or have proper kernel hardening features enabled.
🎯 Exploit Status
Requires local access and ability to trigger UFS driver initialization errors or removal. Exploitation requires precise timing to trigger use-after-free.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Linux kernel with commits 0c77c0d754fe83cb154715fcfec6c3faef94f207, 9c185beae09a3eb85f54777edafa227f7e03075d, f8fb2403ddebb5eea0033d90d9daae4c88749ada applied
Vendor Advisory: https://git.kernel.org/stable/c/0c77c0d754fe83cb154715fcfec6c3faef94f207
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version from your distribution. 2. Reboot system to load new kernel. 3. Verify kernel version after reboot.
🔧 Temporary Workarounds
Disable UFS module
allPrevent loading of vulnerable UFS driver if not needed
echo 'blacklist ufshcd' >> /etc/modprobe.d/blacklist-ufs.conf
rmmod ufshcd
🧯 If You Can't Patch
- Restrict local user access to systems with UFS devices
- Implement kernel hardening features like KASLR and stack protection
🔍 How to Verify
Check if Vulnerable:
Check if UFS module is loaded: lsmod | grep ufshcd. If loaded and kernel version is unpatched, system is vulnerable.Check Version:
uname -rVerify Fix Applied:
Check kernel version includes fix commits or is newer than patched version. Verify UFS module loads without issues.📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages
- UFS driver error messages in dmesg
- Use-after-free warnings in kernel logs
Network Indicators:
- None - local vulnerability only
SIEM Query:
source="kernel" AND ("UFS" OR "ufshcd") AND ("panic" OR "use-after-free" OR "BUG:")