CVE-2019-3773 in FLEXCUBE Private Banking
Summary
by MITRE
Spring Web Services, versions 2.4.3, 3.0.4, and older unsupported versions of all three projects, were susceptible to XML External Entity Injection (XXE) when receiving XML data from untrusted sources.
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Analysis
by VulDB Data Team • 04/25/2021
Spring Web Services represents a critical vulnerability in the form of XML External Entity Injection that affects multiple versions of the framework including 2.4.3, 3.0.4, and older unsupported releases. This vulnerability stems from the improper handling of XML data processing within the web services framework, creating an attack surface where malicious actors can exploit the system's XML parser to execute unauthorized operations. The flaw exists in the core XML processing mechanisms that do not adequately sanitize external entity references, allowing attackers to manipulate XML requests and potentially gain access to internal systems or data. The vulnerability maps directly to CWE-611 which specifically addresses Improper Restriction of XML External Entity Reference, and aligns with ATT&CK technique T1213.002 for Data from Information Repositories, as attackers can leverage this weakness to extract sensitive information through crafted XML payloads. When Spring Web Services processes XML data from untrusted sources, the system fails to properly validate or restrict external entity declarations, enabling attackers to perform various malicious activities including but not limited to server-side request forgery attacks, denial of service conditions, and data exfiltration.
The operational impact of this vulnerability extends beyond simple information disclosure to encompass potential system compromise and unauthorized access to backend resources. Attackers can exploit the XXE vulnerability to access local files on the server, perform port scanning, or even execute commands on the underlying operating system depending on the server configuration and available privileges. The attack vector requires minimal sophistication as it only necessitates sending specially crafted XML data to the vulnerable service, making it particularly dangerous in environments where the framework processes XML data from external sources without proper validation. Organizations using affected versions of Spring Web Services face significant risk exposure, especially in scenarios where the framework handles user-provided XML content or integrates with external services that may introduce malicious XML payloads. The vulnerability can be exploited through various means including direct API calls, web service requests, or any communication channel that processes XML data through the affected framework components.
Mitigation strategies for this vulnerability involve immediate version upgrades to patched releases of Spring Web Services, as well as implementing proper XML parsing configurations that disable external entity processing. Organizations should enforce strict input validation on all XML data received from untrusted sources and configure XML parsers to reject external entity declarations. Security teams must also implement network segmentation and monitoring to detect potential exploitation attempts, while applying the principle of least privilege to limit the impact of successful attacks. The remediation process should include comprehensive testing to ensure that XML processing logic properly handles external entities and that no bypass mechanisms exist in the parsing configuration. Additionally, organizations should consider implementing web application firewalls or XML gateways that can filter out potentially malicious XML content before it reaches the vulnerable framework components. Security controls should be designed to align with industry standards such as OWASP Top Ten and NIST Cybersecurity Framework, ensuring that the mitigation approach addresses both immediate vulnerability remediation and long-term security posture improvement. Regular vulnerability assessments and security audits should be conducted to identify similar weaknesses in other components of the application stack that may be susceptible to similar XXE attack patterns.