SEO Title: AlmaLinux Security Advisory CVE-2026-31431 – “copy_file_range” Vulnerability and Fix Guide

Critical Security Advisory – AlmaLinux (CVE-2026-31431)

We are issuing an important notice regarding a recently disclosed vulnerability affecting AlmaLinux systems.

Official advisory: https://almalinux.org/blog/2026-05-01-cve-2026-31431-copy-fail/

Vulnerability ID: CVE-2026-31431
Severity: High
Component: Linux Kernel (file copy mechanism – copy_file_range)

What is the issue?

This vulnerability is related to the Linux kernel’s copy_file_range function, which is used for copying data between files.

Due to improper handling in certain scenarios, file copy operations may:

• Fail silently

• Result in incomplete or corrupted file copies

• Cause unexpected behavior in applications relying on file operations

This can affect backups, migrations, and any software performing file-level copy tasks.

What is the risk?

While this is not a direct remote exploit, it can still cause serious operational issues:

• Corrupted backups or incomplete restores

• Data inconsistency during migrations

• Application errors when handling files

• Risk of unnoticed data loss

This is especially important for hosting servers handling backups, JetBackup, rsync operations, or storage sync tasks.

Who is affected?

• AlmaLinux systems running affected kernel versions

• Servers performing file copy operations using kernel-level methods

• Backup systems relying on efficient file copy functions

Actions taken by HostRainbow

• Reviewed affected systems across infrastructure

• Ensured kernel updates are applied where required

• Verified backup systems and data integrity

• Monitored file operations and storage behavior

All managed HostRainbow servers are being checked and secured.

Required actions for unmanaged or self-managed servers

If you manage your own VPS or dedicated server, follow these steps:

1. Update system packages and kernel

Run:

dnf update -y

2. Reboot the server (Required)

After updating, reboot to apply the patched kernel:

reboot

3. Verify kernel version

After reboot, confirm the updated kernel:

uname -r

Ensure it reflects the latest patched version provided by AlmaLinux.

4. Verify backup integrity

• Check recent backups for corruption

• Test restore from backup files

• Re-run critical backups if needed

5. Avoid risky file copy operations temporarily

Until fully patched:

• Avoid heavy file migrations

• Be cautious with rsync, cp, and backup tools

• Validate file sizes and checksums after copy

6. Monitor logs for anomalies

Check:

• /var/log/messages

• /var/log/syslog

Look for:

• File operation errors

• Kernel warnings

• Backup-related failures

Important note

If your system was running an affected kernel and performing file operations, there is a possibility of silent data corruption.

Recommended:

• Re-verify critical data

• Re-run backups

• Audit important files and databases

Need assistance?

If you need help verifying your server, updating your system, or checking backup integrity, our support team is available to assist.

Team HostRainbow