Vulnerability details

Recently, foreign security teams announced that a local permission escalation vulnerability has been discovered in the pkexec program of Polkit. The pkexec application is a setuid tool designed to allow non privileged users to run commands as privileged users based on predefined policies.

Due to the current version of pkexec not being able to properly handle call parameter counting, it will eventually attempt to execute environment variables as commands. Attackers can induce pkexec to execute arbitrary code by controlling environment variables. After successful utilization, it can cause non privileged users to gain administrator privileges.

Risk level

High risk

Vulnerability risk

At present, the vulnerability POC has been leaked, and attackers can exploit this vulnerability to cause harm such as malicious user privilege escalation

Impact version

Due to the pre installed tools for the system, mainstream Linux versions are currently affected

Safe version

CentOS series:

CentOS 6: polkit-0.96-11.el6_10.2 (Tencent Cloud is not affected by default)

CentOS 7：polkit-0.112-26.el7_9.1

CentOS 8.0：polkit-0.115-13.el8_5.1

CentOS 8.2：polkit-0.115-11.el8_2.2

CentOS 8.4：polkit-0.115-11.el8_4.2

Ubuntu series:

Repair suggestions

CentOS users can upgrade to a secure version or higher using the following command:

yum clean all && yum makecache

yum update polkit -y

You can check if Polkit is a secure version by using the following command:

rpm -qa polkit

Ubuntu users can upgrade to a secure version or higher using the following command:

sudo apt-get update

sudo apt-get install policykit-1

You can check if Polkit is a secure version by using the following command:

dpkg -l policykit-1

The official source has not been updated, and users can temporarily alleviate it by using the following command:

#Chmod 0755/usr/bin/pkexec

At present, the official Linux distributions have provided security patches. It is recommended that users upgrade to the secure version as soon as possible, or refer to the official instructions to alleviate the situation. CentOS, Ubuntu, and Debian users can refer to the following link:

https://ubuntu.com/security/CVE-2021-4034

https://access.redhat.com/security/cve/CVE-2021-4034

https://security-tracker.debian.org/tracker/CVE-2021-4034

[Note]: It is recommended that you do a good job of data backup before upgrading to avoid accidents