CVE-2020-19954 in S-CMS
Summary
by MITRE • 10/14/2021
An XML External Entity (XXE) vulnerability was discovered in /api/notify.php in S-CMS 3.0 which allows attackers to read arbitrary files.
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Analysis
by VulDB Data Team • 10/20/2021
The vulnerability identified as CVE-2020-19954 represents a critical XML External Entity flaw within the S-CMS 3.0 content management system specifically affecting the /api/notify.php endpoint. This XXE vulnerability stems from the application's improper handling of XML input data, creating a pathway for malicious actors to manipulate the system's XML parser and execute unauthorized operations. The flaw exists in the server-side processing logic where user-supplied XML data is parsed without adequate sanitization or validation mechanisms, allowing attackers to craft malicious XML payloads that can be exploited to access sensitive system resources.
The technical implementation of this vulnerability allows adversaries to leverage the XML parser's capability to resolve external entities and references. When the /api/notify.php script processes XML data containing external entity declarations, it fails to properly restrict access to local file system resources or network endpoints. This creates a scenario where attackers can construct XML payloads that reference local files on the server, enabling arbitrary file read operations. The vulnerability aligns with CWE-611, which specifically addresses Improper Restriction of XML External Entity Reference, and represents a direct violation of secure coding practices for XML processing. Attackers can exploit this by crafting XML requests that include entity declarations pointing to sensitive files such as configuration files, database credentials, or system files that may contain confidential information.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with the capability to escalate their attack and potentially gain deeper system access. Successful exploitation could lead to the extraction of sensitive data including database connection strings, administrator credentials, or other confidential information stored in accessible files. The vulnerability affects the confidentiality and integrity aspects of the system's security posture, as it allows unauthorized data access that could enable further exploitation techniques. Organizations running S-CMS 3.0 are particularly at risk since this vulnerability can be exploited remotely without requiring authentication, making it a high-severity threat that could result in data breaches and system compromise. The attack surface is particularly concerning given that the vulnerability exists in a notification API endpoint, which may be frequently accessed and could be exposed to untrusted inputs from various sources.
Mitigation strategies for CVE-2020-19954 should focus on implementing proper XML parser configuration and input validation measures. The primary remediation involves disabling external entity resolution in the XML parser configuration and implementing strict input validation for all XML data received by the /api/notify.php endpoint. Security measures should include configuring the XML parser to reject any external entity declarations and ensuring that all XML processing occurs within a restricted environment that limits file system access. Organizations should also implement proper access controls and network segmentation to limit exposure of the vulnerable API endpoint. Additionally, regular security updates and patches should be applied to the S-CMS platform to address the underlying vulnerability, while implementing web application firewalls that can detect and block malicious XML payloads targeting this specific vulnerability. The remediation efforts should align with ATT&CK technique T1213.002 for data from information repositories, as this vulnerability enables adversaries to extract sensitive data from system repositories through improper XML processing.