ROS-2-476

2.476 Remote code execution in nginx(CVE-2021-23017)

1. Vulnerability Description:

The vulnerability allows a remote attacker to execute arbitrary code on the target system. The vulnerability exists due to a single error in the ngx_resolver_copy()function when processing DNS responses. A remote attacker could cause a non-unique error, write the dot character (‘.’, 0x2E) out of bounds in the allocated heap buffer, and execute arbitrary code on the system. Successful exploitation of this vulnerability could lead to a complete compromise of the vulnerable system.Identifier of the Information Security Threats Data Bank of the FSTEC of Russia: BDU:2021-02749

2. Possible measures to eliminate the vulnerability

Do not use nginx server or - install security updates for package: nginx**Installing updates is possible in the following ways:**a) if the computer with the installed OS version has access to the vendor’s official repository, run the update as administrator with the command:# yum updateAfter the list of updated packages is displayed, agree to apply the updates by pressing the Y key on the keyboard. Wait until the update installation is complete and make sure that there are no errors during its installation.b)If the computer with the installed OS version does not have access to the vendor’s official repository, you should perform the following actions: - download the updated package (with dependencies if necessary): http://repo.red-soft.ru/redos/7.2c/x86_64/updates/nginx-1.14.1-4.el7.x86_64.rpm Check the integrity and authenticity of the package according to instructionsInstall the downloaded package(s) with the command:# yum localinstall *.rpmWhen the list of updated packages is displayed, agree to apply the updates by pressingY on the keyboard. Wait for the updates to finish installing and make sure there are no errors during the installation.

Date of last modification: 08.09.2021