CVE-2019-9761 in PHPSHE
Summary
by MITRE
An XXE issue was discovered in PHPSHE 1.7, which can be used to read any file in the system or scan the internal network without authentication. This occurs because of the call to wechat_getxml in include/plugin/payment/wechat/notify_url.php.
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Analysis
by VulDB Data Team • 08/01/2023
The vulnerability identified as CVE-2019-9761 represents a critical XML External Entity processing flaw within the PHPSHE 1.7 web application framework. This issue stems from improper input validation in the wechat_getxml function located in the include/plugin/payment/wechat/notify_url.php file, creating an exploitable pathway for attackers to manipulate XML parsing behavior. The vulnerability exists in the context of payment processing functionality where the application accepts XML data from external sources without adequate sanitization measures, making it susceptible to malicious XML entity declarations that can be leveraged for unauthorized system access.
The technical implementation of this vulnerability exploits the inherent weakness in how the application processes XML data through the wechat_getxml function. When the application receives XML input containing external entity references, it fails to properly validate or sanitize these entities before processing, allowing attackers to craft malicious XML payloads that can trigger file system access or network scanning operations. This flaw directly maps to CWE-611, which categorizes improper restriction of XML external entity reference as a critical security weakness. The vulnerability's exploitation enables attackers to perform unauthorized file reads on the server filesystem, potentially accessing sensitive configuration files, database credentials, or other critical system resources that should remain protected from external access.
The operational impact of this vulnerability extends beyond simple information disclosure to encompass potential network reconnaissance and lateral movement capabilities. Attackers can leverage the XXE vulnerability to scan internal network services and systems that are typically not directly exposed to the internet, effectively using the vulnerable application as a pivot point for broader network exploration. This capability aligns with ATT&CK technique T1016, which describes network service scanning as a method for discovering and mapping network infrastructure. The vulnerability's lack of authentication requirements makes it particularly dangerous as it can be exploited by anyone with access to the vulnerable application, potentially allowing for complete system compromise through information gathering and subsequent exploitation of other vulnerabilities.
Mitigation strategies for CVE-2019-9761 require immediate implementation of XML parsing restrictions and input validation measures. Organizations should disable external entity processing in all XML parsers used within the application, particularly in the wechat_getxml function and related payment processing modules. The recommended approach includes implementing proper XML schema validation, sanitizing all external input before processing, and restricting file system access permissions for the application's user account. Additionally, network segmentation should be implemented to limit the potential impact of successful exploitation, and regular security audits should be conducted to identify similar vulnerabilities in other components of the application stack. The fix should also include updating to the latest version of PHPSHE 1.7 where this vulnerability has been patched, as the vendor has addressed the issue through proper input validation and XML parsing restrictions.