CVE-2021-22968 : Security Advisory and Response
Learn about CVE-2021-22968, a vulnerability in Concrete CMS that allows remote code execution in versions 8.5.6 and below. Understand the impact, technical details, and mitigation steps.
A bypass of adding remote files in Concrete CMS (previously concrete5) File Manager leads to remote code execution in Concrete CMS (concrete5) versions 8.5.6 and below. The external file upload feature stages files in the public directory even if they have disallowed file extensions. To fix this, a check for allowed file extensions was added before downloading files to a tmp directory. Concrete CMS Security Team assigned this CVE a CVSS v3.1 score of 5.4.
Understanding CVE-2021-22968
This CVE involves a bypass vulnerability in the File Manager of Concrete CMS (concrete5) that allows remote code execution in specific versions.
What is CVE-2021-22968?
CVE-2021-22968 is a vulnerability in Concrete CMS (previously known as concrete5) that enables an attacker to execute remote code by exploiting the file upload feature.
The Impact of CVE-2021-22968
The vulnerability allows an authenticated admin user to bypass file extension restrictions and upload restricted files, potentially leading to remote code execution depending on server configurations.
Technical Details of CVE-2021-22968
This section dives into the specifics of the vulnerability.
Vulnerability Description
The issue arises from the File Manager's handling of external file uploads, allowing files with disallowed extensions to be staged in a public directory, exposing them to potential exploitation.
Affected Systems and Versions
Concrete CMS versions 8.5.6 and below are impacted by this vulnerability, highlighting the importance of updating to secure versions.
Exploitation Mechanism
An attacker must have admin privileges to upload files, exploiting the flaw to execute restricted file types, depending on server settings.
Mitigation and Prevention
Understanding how to mitigate the risks associated with CVE-2021-22968 is crucial for maintaining cybersecurity.
Immediate Steps to Take
Users should update their Concrete CMS installations to version 9.0.0 or newer, where a fix for this vulnerability has been implemented.
Long-Term Security Practices
Enforcing strict file upload policies, monitoring uploads closely, and regularly updating software are essential long-term security measures.
Patching and Updates
Regularly checking for software updates and promptly applying patches is crucial in preventing exploitation of known vulnerabilities.