Linux ‘Copy Fail’ Vulnerability Grants Root Access on Major Distros

Cybersecurity researchers have revealed a significant vulnerability in the Linux operating system, enabling a local user without privileges to gain root access. This flaw, identified as CVE-2026-31431 and rated with a severity score of 7.8, has been codenamed “Copy Fail” by firms Xint.io and Theori.

The vulnerability arises from a logical error in the Linux kernel’s cryptographic subsystem, specifically within the algif_aead module, which was introduced in a code update in August 2017. This breach permits an unprivileged user to manipulate the page cache of any readable file on a Linux system, effectively allowing them to escalate their privileges to that of a root user.

Exploiting this vulnerability does not require extensive technical knowledge. A simple 732-byte Python script can edit a setuid binary—files that allow users to execute programs with the permissions of the file owner. The exploit follows a series of steps, including opening an AF_ALG socket, constructing a payload, writing to the kernel’s cached copy of “/usr/bin/su,” and executing it to gain root access.

Though the flaw cannot be exploited remotely on its own, a local user can corrupt the page cache of a setuid binary to escalate privileges. This issue poses additional risks as the affected page cache is shared across processes, potentially impacting containerised environments.

In reaction to the discovery, various Linux distributions have issued advisories regarding the vulnerability. Comparisons have been drawn to a previous exploit, Dirty Pipe, which allowed users to overwrite sensitive files on the system. The unique characteristics of Copy Fail, including its portability and stealthiness, enhance its threat level significantly. Furthermore, it allows low-level user accounts to gain full administrative privileges, undermining the integrity of the operating system’s security protocols.

Next steps are likely to involve immediate updates and patches from Linux distributors to mitigate the risks associated with this critical vulnerability.

How much do you know?

What is the severity score of the vulnerability identified as CVE-2026-31431?

5.4

6.1

7.8

9.0

What is the codename given to the vulnerability CVE-2026-31431?

Dirty Pipe

Copy Fail

Kernel Panic

Access Denied

In which year was the flaw in the Linux kernel's cryptographic subsystem introduced?

2015

2016

2017

2018

Which module of the Linux kernel is associated with the vulnerability?

algif_aead

ext4

vfs

tcp

What type of script can exploit the vulnerability with a size of 732 bytes?

Bash script

Python script

Perl script

JavaScript

What is the first step in the exploitation process of the vulnerability?

Writing to setuid binary

Opening an AF_ALG socket

Executing payload

Editing kernel cache

The vulnerability CVE-2026-31431 allows for remote exploitation.

True False

Copy Fail permits unprivileged users to gain root access on Linux systems.

True False

The page cache affected by Copy Fail is unique to each process.

True False

Linux distributions have not issued advisories regarding the Copy Fail vulnerability.

True False

A simple Python script is needed to exploit the Copy Fail vulnerability.

True False

The severity score of the Copy Fail vulnerability is more than 8.

True False

The logical error in the Linux kernel's cryptographic subsystem is located within the algifaead module, which was introduced in a code update in August .

The exploit allows a local user to manipulate the page cache of any readable file, escalating their privileges to that of a user.

A simple -byte Python script can edit a setuid binary to exploit the vulnerability.

Exploiting the flaw requires a local user to corrupt the page cache of a setuid to escalate privileges.

The unique characteristics of Copy Fail, including its portability and stealthiness, enhance its level significantly.

Immediate updates and from Linux distributors are likely next steps to mitigate risks associated with the vulnerability.

This question is required