CVE-2020-26564 in Opinio
Summary
by MITRE • 07/31/2021
ObjectPlanet Opinio before 7.15 allows XXE attacks via three steps: modify a .css file to have
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Analysis
by VulDB Data Team • 08/06/2021
CVE-2020-26564 represents a critical server-side request forgery vulnerability in ObjectPlanet Opinio versions prior to 7.15 that enables attackers to execute XML External Entity attacks through a multi-stage exploitation process. This vulnerability falls under the CWE-611 weakness category, specifically addressing insecure direct object references and XML external entity processing flaws. The attack vector involves manipulating a .css file to include malicious XML entities that can trigger unauthorized access to internal resources. The vulnerability exists due to insufficient input validation and sanitization within the application's processing of CSS files, which are subsequently parsed by an XML parser that does not properly restrict external entity resolution. Attackers can leverage this flaw to access sensitive internal systems, perform port scanning, or retrieve confidential data from the server. The three-step modification process typically begins with uploading or modifying a CSS file that contains crafted XML entities, followed by a second step that forces the application to process this file through its XML parsing mechanism, and concludes with a third step that executes the malicious payload. This vulnerability aligns with ATT&CK technique T1059.007 for XML external entity attacks and T1046 for network service scanning. The operational impact extends beyond simple data exfiltration as it can provide attackers with persistent access to internal network resources and potentially enable further lateral movement within the affected environment.
The technical implementation of this vulnerability demonstrates a classic case of improper input handling where CSS files are not properly sanitized before being processed by the application's XML parser. The flaw occurs because the application treats CSS files as trusted content without validating their structure or content against a whitelist of acceptable elements. When the application processes these files through an XML parser that supports external entity resolution, it inadvertently allows attackers to specify external resources that can be accessed and potentially exploited. This represents a fundamental security issue in the application's architecture where different data processing pipelines are not properly isolated from each other. The vulnerability is particularly concerning because CSS files are commonly used in web applications and are often uploaded by users with varying permission levels, creating an attack surface that can be exploited through simple file manipulation. The attack requires minimal privileges and can be executed through standard web application interfaces, making it highly accessible to attackers with basic web application exploitation skills.
Mitigation strategies for CVE-2020-26564 should focus on implementing comprehensive input validation and sanitization measures across all user-uploaded content processing pipelines. Organizations should immediately upgrade to ObjectPlanet Opinio version 7.15 or later, which includes proper XML external entity handling and input validation. Security measures must include disabling external entity resolution in all XML parsers used by the application, implementing strict content type validation for uploaded files, and establishing proper file access controls. Network-level protections should include monitoring for unusual XML parsing activities and implementing web application firewalls that can detect and block malicious entity references. The solution approach should also incorporate principle of least privilege for file upload operations, ensuring that uploaded files are stored in isolated directories with restricted access permissions. Additionally, regular security testing should include XML entity injection testing to identify similar vulnerabilities in other components of the application stack. Organizations should also implement proper logging and monitoring of file processing activities to detect potential exploitation attempts. This vulnerability highlights the importance of comprehensive security testing across all application components, particularly those handling user-supplied content and external data processing functions. The remediation process should include thorough code review of all XML processing functions and implementation of automated security scanning tools to prevent similar vulnerabilities from being introduced in future development cycles.