The CopyFail vulnerability (CVE-2026-31431) has been shaking the Linux world since its discovery in late April. This vulnerability allows for critical local privilege escalation, granting root access from a simple user account. But what is the current status of patch distribution? It’s best to know to avoid unpleasant surprises.
The security implications of the CopyFail vulnerability on Linux
CopyFail affects the cryptographic subsystem of the Linux kernel, more specifically the module algif_aeadThis vulnerability, present since 2017, allows an unprivileged user to gain root privileges. It is particularly insidious because it can be exploited locally or remotely if another vulnerability is present on the system, such as a poorly patched CMS.
The danger is real: a privilege escalation on a Linux server is like leaving the barn door open in a strong wind. Once an attacker gets through, chaos can spread rapidly.
The Linux kernel versions affected by the vulnerability
Good news: the Linux kernel since version 7.0 is beyond the reach of CopyFail. This means that the problem primarily affects the 5.x and 6.x branches, which are often used in current deployments. The most widely used LTS versions are affected, meaning that many popular distributions need to take action.
The fixes have been integrated into the following branches:
- 6.12 LTS via version 6.12.85
- 6.6 LTS via version 6.6.137
- 6.1 LTS in version 6.1.170
- 5.15 LTS in version 5.15.204
- 5.10 LTS in version 5.10.254
However, vigilance remains essential: end-of-life kernels like 6.17 or 6.19 can still reveal this vulnerability, impacting in particular recent versions of distributions like Ubuntu 25.10.
What is the current status of patch availability for major Linux distributions?
The complexity here stems from the diversity of kernels embedded in each distribution. Each maintainer must therefore backport and test the patch on their specific version. This step sometimes slows down the process and explains the still uneven deployment.
To date, several distributions have released their fixes:
Concrete examples of deployment
Debian has covered its Bullseye, Bookworm, Trixie, and Sid versions with the fixes integrated into kernel versions ranging from 5.10.251 to 7.0.3. To apply the update, a simple sudo apt update && sudo apt upgrade followed by a restart is sufficient.
Ubuntu deployed a temporary mitigation by disabling the vulnerable module via a package update kmodThe final kernel patch is being deployed, especially for versions prior to the resolved 26.04.
AlmaLinux has already delivered a corrected kernel for its versions 8, 9 and 10, which offers a real example of responsiveness in an Enterprise context.
CopyFail fixes on NAS: a more mixed picture
For users of NAS devices, the situation is mixed. It depends heavily on the hardware architecture and the manufacturer’s policy.
QNAP is currently lagging behind some ARM64 versions incorporating a vulnerable 5.10 kernel, while Synology declares not to be concerned. On the other hand ASUSTORNo public information has emerged so far.
How to check and patch your Linux kernel on Debian 13
For an administrator running Debian 13, applying the patch is a simple operation, although a reboot is required. After updating with sudo apt update && sudo apt upgrade, a kernel check via uname -r will confirm the correct version.
If the displayed version is not the expected 6.12.85-1, it means a restart is necessary. This final step is sometimes overlooked, so keep an eye out.