CVE-2021-44123 in SPIP
Summary
by MITRE • 01/26/2022
SPIP 4.0.0 is affected by a remote command execution vulnerability. To exploit the vulnerability, an attacker must craft a malicious picture with a double extension, upload it and then click on it to execute it.
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Analysis
by VulDB Data Team • 01/29/2022
The vulnerability identified as CVE-2021-44123 affects SPIP version 4.0.0 and represents a critical remote command execution flaw that can be exploited through improper file validation mechanisms. This vulnerability stems from insufficient input sanitization during file upload processes, particularly when handling image files with deceptive naming conventions. The attack vector specifically targets the content management system's file handling capabilities where malicious actors can manipulate file extensions to bypass security controls.
The technical implementation of this vulnerability relies on the exploitation of double extension file uploads, a well-documented technique where files are named with two extensions such as image.jpg.php, where the system processes the first extension while the second extension contains executable code. In the context of SPIP 4.0.0, when an attacker uploads such a malicious file and subsequently triggers its execution through clicking on the uploaded image, the system's inadequate validation allows the secondary payload to execute with the privileges of the web application. This flaw directly maps to CWE-434 which describes insecure file upload vulnerabilities where systems accept files without proper validation of their content or extension.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with complete control over the affected system. Once executed, the malicious payload can perform arbitrary commands on the server, potentially leading to data theft, system compromise, or further lateral movement within the network. The vulnerability's exploitation requires minimal privileges and can be automated, making it particularly dangerous in environments where SPIP is used for content management. According to ATT&CK framework, this vulnerability corresponds to T1059.001 for command and scripting interpreter and T1566.001 for malicious file execution, demonstrating how attackers can leverage such flaws to establish persistent access.
Mitigation strategies for CVE-2021-44123 should focus on implementing robust file validation mechanisms that enforce strict content type checking rather than relying solely on file extension validation. Organizations should implement mandatory file type verification using MIME type detection, content analysis, and proper file extension filtering. The system should reject any files that do not conform to expected content types or contain suspicious patterns. Additionally, implementing proper file upload restrictions including limiting upload directories, using randomized file names, and disabling execution permissions on upload locations would significantly reduce the risk. Regular security updates and patches should be applied immediately upon availability, as the vulnerability affects a specific version of the software that has known remediation paths. The implementation of web application firewalls and content security policies can also provide additional layers of protection against such exploitation attempts.