CVE-2018-20318 in weixin-java-tools
Summary
by MITRE
An issue was discovered in weixin-java-tools v3.2.0. There is an XXE vulnerability in the getXmlDoc method of the BaseWxPayResult.java file.
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Analysis
by VulDB Data Team • 06/20/2023
The vulnerability identified as CVE-2018-20318 represents a critical XML External Entity processing weakness within the weixin-java-tools library version 3.2.0. This library serves as a Java SDK for WeChat payment integration and other WeChat platform functionalities, making it a widely used component in enterprise applications that handle WeChat payments and related services. The vulnerability specifically resides in the BaseWxPayResult.java file within the getXmlDoc method, which processes XML responses from WeChat payment APIs. The flaw enables malicious actors to exploit the XML parsing mechanism and potentially execute unauthorized operations through carefully crafted XML payloads that reference external entities or perform server-side request forgery attacks.
This XXE vulnerability falls under CWE-611, which categorizes it as an Improper Restriction of XML External Entity Reference. The technical implementation of this flaw allows attackers to manipulate the XML parsing process by including external entity declarations within XML documents that the application processes. When the getXmlDoc method parses XML content containing malicious entity references, the underlying XML parser may resolve these external references, leading to information disclosure, denial of service, or potentially remote code execution depending on the target environment and the capabilities of the XML parser being used. The vulnerability is particularly concerning because it affects a core component of payment processing functionality, potentially allowing attackers to access sensitive payment data or disrupt payment services.
The operational impact of this vulnerability extends beyond simple data exposure, as it could enable attackers to perform server-side request forgery attacks that might allow them to access internal systems or services that are typically protected from external access. In payment processing contexts, this could result in unauthorized access to payment transaction data, financial information, or even facilitate fraudulent transactions. The vulnerability affects organizations that integrate WeChat payment functionality into their applications, potentially exposing them to data breaches, financial losses, and compliance violations. Security assessments reveal that the attack surface is significant given the widespread adoption of weixin-java-tools in enterprise payment solutions, with many organizations unknowingly exposing their systems to potential exploitation.
Organizations affected by this vulnerability should immediately upgrade to a patched version of weixin-java-tools that properly sanitizes XML input and disables external entity processing. The recommended mitigation strategy includes implementing proper XML parsing configurations that disable external entity resolution and DTD processing, which aligns with the ATT&CK framework's defense techniques for preventing XML external entity attacks. Additionally, network segmentation and monitoring of payment processing systems can help detect and prevent exploitation attempts. Security teams should also conduct comprehensive vulnerability assessments to identify all instances where the affected library is used and ensure that proper input validation and sanitization measures are implemented throughout the application architecture to prevent similar issues in other components.