CVE-2017-11628 in PHP
Summary
by MITRE
In PHP before 5.6.31, 7.x before 7.0.21, and 7.1.x before 7.1.7, a stack-based buffer overflow in the zend_ini_do_op() function in Zend/zend_ini_parser.c could cause a denial of service or potentially allow executing code. NOTE: this is only relevant for PHP applications that accept untrusted input (instead of the system's php.ini file) for the parse_ini_string or parse_ini_file function, e.g., a web application for syntax validation of php.ini directives.
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Analysis
by VulDB Data Team • 12/14/2022
The vulnerability identified as CVE-2017-11628 represents a critical stack-based buffer overflow affecting multiple PHP versions including 5.6.x before 5.6.31, 7.0.x before 7.0.21, and 7.1.x before 7.1.7. This flaw resides within the zend_ini_do_op() function located in Zend/zend_ini_parser.c, making it particularly dangerous for web applications that process untrusted input through the parse_ini_string or parse_ini_file functions. The vulnerability stems from inadequate bounds checking during the parsing of ini-style configuration data, creating a scenario where malicious input can overwrite adjacent stack memory regions. Such buffer overflow conditions typically arise when an application writes more data to a fixed-length buffer than it can accommodate, potentially leading to memory corruption that manifests as program termination or unauthorized code execution.
The operational impact of this vulnerability extends beyond simple denial of service to encompass potential code execution capabilities, making it a severe threat to web application security. When applications utilize the parse_ini_string or parse_ini_file functions to process user-supplied configuration data, they become susceptible to exploitation by attackers who craft malicious input designed to trigger the buffer overflow. The vulnerability's relevance is specifically tied to applications that accept untrusted input rather than system php.ini files, which means web-based configuration validators or parsers become primary attack vectors. This characteristic aligns with CWE-121 Stack-based Buffer Overflow, a well-documented weakness where insufficient bounds checking allows data to overwrite adjacent memory locations, potentially corrupting program execution flow.
Security practitioners must recognize that this vulnerability directly relates to the ATT&CK technique T1059.007 Command and Scripting Interpreter: Python, though more accurately maps to T1203 Exploitation for Client Execution and T1068 Exploitation of Remote Services. The attack surface expands significantly when considering that many web applications implement configuration parsing functionality to validate user input or process uploaded configuration files. The buffer overflow can be triggered through specially crafted ini-style input that causes the zend_ini_do_op() function to write beyond allocated stack space, potentially allowing attackers to manipulate program execution flow or cause system instability. This vulnerability particularly affects applications that provide configuration validation services or allow users to upload custom ini files for processing, creating a direct pathway for privilege escalation or complete system compromise.
Mitigation strategies for CVE-2017-11628 primarily focus on immediate version upgrades to patched PHP releases, with the affected versions requiring updates to PHP 5.6.31, 7.0.21, or 7.1.7 respectively. Organizations should implement input validation measures to prevent untrusted data from reaching the vulnerable parse_ini_string and parse_ini_file functions, including sanitizing all user-supplied configuration data before processing. Additional protective measures include deploying application firewalls, implementing strict input validation routines, and conducting thorough code reviews to identify any other potential uses of vulnerable functions within the application stack. The vulnerability's exploitation requires specific conditions where user input is processed through the affected PHP functions, making proper input sanitization and validation essential defensive measures. Security monitoring should specifically track usage of these functions in applications that handle external configuration input, as this represents the primary attack vector for leveraging this buffer overflow vulnerability.