CVE-2025-21727
📋 TL;DR
This is a use-after-free vulnerability in the Linux kernel's padata subsystem that allows an attacker with local access to potentially crash the system or execute arbitrary code. It affects Linux systems using parallel cryptographic processing via the padata framework. The vulnerability occurs when cryptographic algorithms are deleted while parallel processing is still in progress.
💻 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
Local privilege escalation to kernel-level code execution, leading to complete system compromise, data theft, or persistent backdoor installation.
Likely Case
Kernel panic or system crash causing denial of service, potentially leading to data corruption or system instability.
If Mitigated
Minimal impact if proper access controls prevent local attackers from accessing the system or if the padata subsystem is not in use.
🎯 Exploit Status
Exploitation requires local access and knowledge of the padata subsystem. The vulnerability was discovered through LTP testing and can be reproduced with specific timing conditions.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Linux kernel versions with commits 0ae2f332cfd2d74cf3ce344ec9938cf3e29c3ccd or later
Vendor Advisory: https://git.kernel.org/stable/c/0ae2f332cfd2d74cf3ce344ec9938cf3e29c3ccd
Restart Required: Yes
Instructions:
1. Update to a patched Linux kernel version from your distribution's repositories. 2. Reboot the system to load the new kernel. 3. Verify the kernel version after reboot. For custom kernels, apply the fix commit and rebuild.
🔧 Temporary Workarounds
Disable padata subsystem
allRemove or disable the padata module if not required for system functionality
modprobe -r padata
echo 'blacklist padata' >> /etc/modprobe.d/blacklist.conf
Restrict access to cryptographic operations
allLimit which users can perform cryptographic operations that use the padata subsystem
🧯 If You Can't Patch
- Implement strict access controls to prevent unauthorized local users from accessing the system
- Monitor for kernel crashes or unusual system behavior that might indicate exploitation attempts
🔍 How to Verify
Check if Vulnerable:
Check kernel version with 'uname -r' and compare against affected versions. Systems using kernel versions before the fix commits are vulnerable if padata is in use.Check Version:
uname -rVerify Fix Applied:
Verify kernel version is patched (post-fix commits) and check that system remains stable during parallel cryptographic operations.📡 Detection & Monitoring
Log Indicators:
- Kernel panic logs
- KASAN reports of use-after-free in padata functions
- System crashes during cryptographic operations
Network Indicators:
- None - this is a local vulnerability
SIEM Query:
Search for kernel panic events, KASAN reports, or system crash logs mentioning padata_reorder or padata_find_next🔗 References
- https://git.kernel.org/stable/c/0ae2f332cfd2d74cf3ce344ec9938cf3e29c3ccd
- https://git.kernel.org/stable/c/573ac9c70bf7885dc85d82fa44550581bfc3b738
- https://git.kernel.org/stable/c/80231f069240d52e98b6a317456c67b2eafd0781
- https://git.kernel.org/stable/c/bbccae982e9fa1d7abcb23a5ec81cb0ec883f7de
- https://git.kernel.org/stable/c/e01780ea4661172734118d2a5f41bc9720765668
- https://git.kernel.org/stable/c/f3e0b9f790f8e8065d59e67b565a83154d9f3079
- https://git.kernel.org/stable/c/f78170bee51469734b1a306a74fc5f777bb22ba6
- https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html
- https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html
