CVE-2011-2202 in PHP
Summary
by MITRE
The rfc1867_post_handler function in main/rfc1867.c in PHP before 5.3.7 does not properly restrict filenames in multipart/form-data POST requests, which allows remote attackers to conduct absolute path traversal attacks, and possibly create or overwrite arbitrary files, via a crafted upload request, related to a "file path injection vulnerability."
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Analysis
by VulDB Data Team • 11/27/2024
The vulnerability identified as CVE-2011-2202 represents a critical file path injection flaw in the PHP web application scripting language that affected versions prior to 5.3.7. This vulnerability resides within the rfc1867_post_handler function located in the main/rfc1867.c source file, which processes multipart/form-data POST requests commonly used for file uploads in web applications. The flaw stems from insufficient validation and sanitization of filename parameters within these requests, creating a pathway for malicious actors to manipulate the file system operations during upload processes.
The technical implementation of this vulnerability exploits the lack of proper input validation when processing file upload requests that follow the RFC 1867 specification for file uploads. When PHP receives a multipart/form-data request containing file uploads, the rfc1867_post_handler function is responsible for parsing the request and handling file storage operations. However, the function fails to adequately sanitize filename components that may contain directory traversal sequences such as "../" or absolute path references. This omission allows attackers to inject malicious path components into the filename parameter, potentially enabling them to specify arbitrary file paths where uploaded files should be stored.
The operational impact of this vulnerability is severe and multifaceted, encompassing both unauthorized file system access and potential system compromise. Attackers can leverage this vulnerability to perform absolute path traversal attacks that may result in creating or overwriting arbitrary files on the target system. This capability extends beyond simple file manipulation to potentially allow attackers to overwrite critical system files, inject malicious code into existing files, or create backdoor access points within the web server environment. The vulnerability particularly affects web applications that permit user-uploaded files without proper validation, making it a significant concern for any PHP-based web infrastructure.
Security practitioners should recognize this vulnerability as a variant of CWE-22, which specifically addresses path traversal flaws in file system operations. The ATT&CK framework categorizes this type of vulnerability under T1059.007 for command and scripting interpreter, as attackers may use file manipulation capabilities to establish persistent access or execute malicious payloads. Organizations should implement immediate mitigations including upgrading to PHP version 5.3.7 or later, where this vulnerability has been addressed through enhanced input validation and sanitization of filename parameters. Additional protective measures include implementing strict file upload validation, restricting write permissions on web server directories, and employing web application firewalls to monitor and filter suspicious upload requests containing potentially malicious path components.
The remediation approach for this vulnerability requires comprehensive system hardening and security configuration practices. PHP installations should be updated to versions that include the patched rfc1867_post_handler function with proper filename validation mechanisms. System administrators must also implement robust input validation at multiple layers, including web application level checks, server configuration restrictions, and network-level monitoring to detect anomalous file upload patterns. Furthermore, organizations should conduct regular security assessments of their PHP applications to identify similar vulnerabilities in custom code or third-party components that may exhibit analogous path traversal weaknesses.