CVE-2025-21893
📋 TL;DR
This is a use-after-free vulnerability in the Linux kernel's key management subsystem. When a cryptographic key's reference count reaches zero, the garbage collector may free it while key_put() still attempts to access it, potentially leading to memory corruption. This affects all Linux systems using the kernel's keyring functionality.
💻 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 →⚠️ Risk & Real-World Impact
Worst Case
Kernel panic, system crash, or potential privilege escalation leading to full system compromise if an attacker can trigger the UAF to execute arbitrary code in kernel context.
Likely Case
System instability, crashes, or denial of service due to kernel memory corruption.
If Mitigated
Minimal impact if systems are patched or don't heavily use keyring functionality.
🎯 Exploit Status
Requires local access and ability to manipulate key references. Exploitation would need to overcome kernel memory protections like KASLR and SMAP/SMEP.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Patches available in stable kernel trees via provided git commits
Vendor Advisory: https://git.kernel.org/stable/c/6afe2ea2daec156bd94ad2c5a6f4f4c48240dcd3
Restart Required: Yes
Instructions:
1. Update to a patched kernel version from your distribution vendor. 2. Rebuild kernel if using custom kernel. 3. Reboot system to load new kernel.
🔧 Temporary Workarounds
Disable keyring functionality
allRemove or disable kernel modules and services that use keyring functionality (not recommended as this breaks many security features)
🧯 If You Can't Patch
- Restrict local user access and monitor for suspicious keyring operations
- Implement strict SELinux/AppArmor policies to limit keyring access
🔍 How to Verify
Check if Vulnerable:
Check kernel version and compare with distribution's patched versions. Vulnerable if using unpatched kernel with keyring support.Check Version:
uname -rVerify Fix Applied:
Verify kernel version includes the fix commits: 6afe2ea2daec156bd94ad2c5a6f4f4c48240dcd3 or related patches📡 Detection & Monitoring
Log Indicators:
- Kernel oops messages
- System crashes
- Keyring-related errors in dmesg
SIEM Query:
Search for kernel panic events or keyring-related error messages in system logs