CVE-2022-21829 in Concrete
Summary
by MITRE • 06/24/2022
Concrete CMS Versions 9.0.0 through 9.0.2 and 8.5.7 and below can download zip files over HTTP and execute code from those zip files which could lead to an RCE. Fixed by enforcing ‘concrete_secure’ instead of ‘concrete’. Concrete now only makes requests over https even a request comes in via http. Concrete CMS security team ranked this 8 with CVSS v3.1 vector: AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H Credit goes to Anna for reporting HackerOne 1482520.
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Analysis
by VulDB Data Team • 07/14/2022
The vulnerability CVE-2022-21829 represents a critical remote code execution flaw in Concrete CMS versions 9.0.0 through 9.0.2 and 8.5.7 and below. This security weakness stems from the application's improper handling of zip file downloads and execution processes, creating a pathway for attackers to gain unauthorized system access. The vulnerability operates through a combination of insecure HTTP downloads and code execution mechanisms that were not properly secured in the affected versions. The flaw allows malicious actors to exploit the system's trust in local file operations, particularly when processing zip archives containing malicious payloads.
The technical implementation of this vulnerability involves the concrete and concrete_secure configuration parameters that control how the CMS handles external file operations. In the vulnerable versions, the system defaulted to using 'concrete' which permitted insecure HTTP connections and execution of downloaded code without proper validation. This configuration creates a dangerous attack surface where an authenticated user with sufficient privileges can manipulate the system into downloading and executing arbitrary code from remote servers. The vulnerability's severity is amplified by the fact that it requires minimal user interaction beyond establishing authentication, making it particularly dangerous in environments where administrative access might be compromised.
The operational impact of CVE-2022-21829 extends far beyond simple code execution capabilities, as it provides attackers with complete system compromise potential. An attacker who gains access to an authenticated session can leverage this vulnerability to execute arbitrary commands on the server, potentially leading to full system takeover, data exfiltration, or deployment of additional malicious tools. The CVSS v3.1 score of 8.0 indicates high severity with attack complexity being high but requiring only authenticated access, and the scope being changed, meaning the vulnerability can affect the entire system rather than just the application itself. This aligns with CWE-20, which describes improper input validation, and represents a classic privilege escalation scenario that can be exploited through the principle of least privilege violations in web application security.
The remediation approach for this vulnerability involves enforcing the 'concrete_secure' configuration parameter which mandates HTTPS connections for all file operations, eliminating the possibility of man-in-the-middle attacks during zip file downloads. This fix directly addresses the root cause by ensuring that all communications occur over encrypted channels and that code execution is only permitted from verified secure sources. The Concrete CMS security team's response demonstrates proper vulnerability management through coordinated disclosure and immediate patch development. Organizations should implement this security update immediately, as the vulnerability affects multiple major versions of the CMS and the attack vector requires only authenticated access to exploit. The fix also aligns with ATT&CK technique T1059.007 for command and scripting interpreter, specifically through the use of Windows Command Shell, as the vulnerability enables attackers to execute system commands through the compromised CMS infrastructure.
This vulnerability highlights the importance of secure configuration management and proper input validation in content management systems. The issue demonstrates how seemingly minor configuration parameters can create critical security gaps, particularly when dealing with file download and execution mechanisms. Organizations running Concrete CMS should conduct immediate security assessments to ensure all instances have been updated to versions that enforce secure protocols, and should implement additional monitoring for suspicious file download activities. The vulnerability serves as a reminder of the critical need for regular security updates and the importance of maintaining secure default configurations in web applications.