Copy Fail Vulnerability - CVE-2026-31431

Incident Report for CloudLinux

Update

We've published a blog post with a lot of up-to-date information on the issue
CVE-2026-31431 (Copy Fail): Mitigation and Upcoming Patches for CloudLinux
Posted Apr 30, 2026 - 16:54 UTC

Update

A temporary workaround has been found

It prevents the algif_aead_init() initialization function from being called during kernel boot.
Please note that applying this workaround requires a reboot!

What needs to be done:
grubby --update-kernel=ALL --args="initcall_blacklist=algif_aead_init"
reboot
Posted Apr 30, 2026 - 16:35 UTC

Investigating

Copy Fail (CVE-2026-31431) is a Linux kernel bug in the crypto component authencesn. It allows a normal local user to make a very specific 4-byte change to the cached contents of any readable file on the system. In practice, that means a small Python script could tamper a setuid binary and gain root access on most major Linux distros shipped since 2017.

We're investigating the situation and a patch is on its way for CloudLinux kernels and KernelCare.
Posted Apr 29, 2026 - 21:34 UTC
This incident affects: CloudLinux OS Components (CloudLinux Kernel).