CVE-2025-38221
📋 TL;DR
This CVE-2025-38221 is an out-of-bounds vulnerability in the Linux kernel's ext4 filesystem that occurs when punching holes with invalid offsets. It can cause kernel crashes (denial of service) and potentially lead to data corruption. Any system using the affected Linux kernel versions with ext4 filesystems is vulnerable.
💻 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 →⚠️ Risk & Real-World Impact
Worst Case
Kernel panic leading to system crash and denial of service, with potential data corruption or loss on affected filesystems.
Likely Case
System crash/denial of service when specific file operations are performed on ext4 filesystems with malformed parameters.
If Mitigated
No impact if the vulnerability is patched or if the specific file operations aren't performed.
🎯 Exploit Status
Exploitation requires local access and ability to perform specific filesystem operations. The provided reproducer shows how to trigger the crash.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in kernel commits: 28b62cb58fd014338f5004170f2e3a35bf0af238, a4d60ba277ecd8a98c5a593cbc0ef2237c20a541, b5e58bcd79625423487fa3ecba8e8411b5396327
Vendor Advisory: https://git.kernel.org/stable/c/28b62cb58fd014338f5004170f2e3a35bf0af238
Restart Required: Yes
Instructions:
1. Update Linux kernel to version containing the fix commits. 2. Check your distribution's security advisories for specific patched kernel versions. 3. Reboot system after kernel update.
🔧 Temporary Workarounds
Restrict filesystem operations
linuxLimit users' ability to perform truncate and hole punching operations on critical ext4 filesystems.
Use filesystem ACLs or mount options to restrict write operations
Implement mandatory access controls (SELinux/AppArmor) to limit file operations
🧯 If You Can't Patch
- Monitor for crash reports related to ext4 filesystem operations
- Restrict user access to perform advanced filesystem operations on production systems
🔍 How to Verify
Check if Vulnerable:
Check kernel version and compare with distribution's security advisories. The vulnerability can be tested by attempting the reproducer commands on a test system.Check Version:
uname -rVerify Fix Applied:
Verify kernel version includes the fix commits or check with distribution's security update verification tools.📡 Detection & Monitoring
Log Indicators:
- Kernel panic/Oops messages mentioning ext4_punch_hole, truncate_inode_partial_folio, or zero_user_segments
- System crash logs following filesystem operations
Network Indicators:
- None - this is a local filesystem vulnerability
SIEM Query:
Search for kernel panic events or system crash reports with ext4-related function names in call traces