CVE-2025-21726 – This CVE describes a use-after-free vulnerabili... (How to Fix)

Q: What is the severity of CVE-2025-21726?

CVE-2025-21726 has a CVSS score of 7.8 (HIGH). This CVE describes a use-after-free vulnerability in the Linux kernel's padata subsystem, which is used for parallel data processing. An attacker could potentially exploit this to cause kernel memory corruption, leading to system crashes or privilege escalation. All Linux systems using the padata subsystem are affected.

📋 TL;DR

This CVE describes a use-after-free vulnerability in the Linux kernel's padata subsystem, which is used for parallel data processing. An attacker could potentially exploit this to cause kernel memory corruption, leading to system crashes or privilege escalation. All Linux systems using the padata subsystem are affected.

💻 Affected Systems

Products:

Linux kernel

Versions: Kernel versions with padata subsystem before the fix commits

Operating Systems: All Linux distributions

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects systems using padata subsystem (commonly used for crypto acceleration)

📦 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...

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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 leading to denial of service, or potential privilege escalation to root if combined with other vulnerabilities

🟠

Likely Case

System instability, crashes, or denial of service affecting crypto operations

🟢

If Mitigated

Minimal impact with proper kernel hardening and isolation

🌐 Internet-Facing: LOW - Requires local access or ability to trigger crypto operations

🏢 Internal Only: MEDIUM - Local users or processes could potentially trigger the vulnerability

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires local access and ability to trigger specific padata operations; race condition makes exploitation challenging

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions containing commits: 4c6209efea2208597dbd3e52dc87a0d1a8f2dbe1, 6f45ef616775b0ce7889b0f6077fc8d681ab30bc, 7000507bb0d2ceb545c0a690e0c707c897d102c2, 8ca38d0ca8c3d30dd18d311f1a7ec5cb56972cac, a54091c24220a4cd847d5b4f36d678edacddbaf0

Vendor Advisory: https://git.kernel.org/stable/c/4c6209efea2208597dbd3e52dc87a0d1a8f2dbe1

Restart Required: Yes

Instructions:

1. Update Linux kernel to version containing the fix commits. 2. Reboot system. 3. Check kernel version to confirm update.

🔧 Temporary Workarounds

Disable padata subsystem

all

Remove padata module if not required

rmmod padata

🧯 If You Can't Patch

Restrict local user access to systems
Monitor for kernel panics or unusual crypto subsystem behavior

🔍 How to Verify

Check if Vulnerable:

Check kernel version and if padata module is loaded: lsmod | grep padata

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version includes fix commits and test padata operations

📡 Detection & Monitoring

Log Indicators:

Kernel panic logs
Oops messages related to padata
Crypto subsystem errors

Network Indicators:

None - local vulnerability only

SIEM Query:

search 'kernel panic' OR 'Oops' OR 'padata' in system logs

📊 Metadata

CVE ID: CVE-2025-21726

CVSS v3 Score: 7.8 (HIGH)

CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CWE: CWE-416

EPSS Score: 0.04% exploit probability (12.3th percentile)

Published: February 27, 2025

Last Updated: November 3, 2025

🔗 References

📤 Share & Export

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