CVE-2017-14949 in Restlet
Summary
by MITRE
Restlet Framework before 2.3.12 allows remote attackers to access arbitrary files via a crafted REST API HTTP request that conducts an XXE attack, because only general external entities (not parameter external entities) are properly considered. This is related to XmlRepresentation, DOMRepresentation, SaxRepresentation, and JacksonRepresentation.
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Analysis
by VulDB Data Team • 12/11/2019
The CVE-2017-14949 vulnerability represents a critical server-side request forgery issue within the Restlet Framework version 2.3.11 and earlier. This vulnerability specifically affects applications that process XML representations through various representation classes including XmlRepresentation, DOMRepresentation, SaxRepresentation, and JacksonRepresentation. The flaw stems from improper handling of external entity declarations in XML processing, creating a pathway for remote attackers to exploit XML external entity injection attacks. Attackers can craft malicious HTTP requests that leverage XML parsing mechanisms to access arbitrary files on the server filesystem, potentially leading to data exfiltration, system compromise, or further lateral movement within the network infrastructure.
The technical root cause of this vulnerability lies in the framework's XML parser configuration which fails to properly validate and restrict external entity references. When the Restlet Framework processes XML content through the affected representation classes, it only considers general external entities rather than parameter external entities during XML parsing operations. This incomplete validation allows attackers to construct XML payloads that reference external entities pointing to local files or network resources. The vulnerability is classified under CWE-611 Information Exposure Through XML External Entity Attack, which specifically addresses the risks associated with improper XML entity handling. This weakness creates a direct pathway for attackers to perform unauthorized file access and potentially execute arbitrary code depending on the server's file permissions and system configuration.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can enable attackers to access sensitive system files, configuration data, and potentially compromise the entire application server. When exploited, the XXE attack can lead to unauthorized access to database connection strings, application credentials, and other sensitive information stored in configuration files. The vulnerability is particularly dangerous in cloud environments or multi-tenant applications where the compromise of one service could potentially impact other applications running on the same infrastructure. Organizations using Restlet Framework in production environments face significant risk of data breaches, regulatory compliance violations, and potential system compromise. The attack vector is particularly insidious because it requires minimal privileges and can be executed through standard HTTP requests, making it difficult to detect and prevent without proper input validation and security monitoring.
Mitigation strategies for CVE-2017-14949 focus on updating to Restlet Framework version 2.3.12 or later, which properly addresses the external entity handling issue. Organizations should implement comprehensive XML input validation and sanitization measures, including disabling external entity resolution entirely for XML processing operations. Network security controls such as web application firewalls and intrusion detection systems should be configured to monitor for suspicious XML content patterns and malformed requests. Security teams should also conduct thorough code reviews to identify any custom implementations that might be vulnerable to similar XXE attacks. The remediation process should include updating all affected applications and services, implementing proper input validation at multiple layers, and establishing monitoring procedures to detect potential exploitation attempts. Additionally, organizations should follow ATT&CK framework techniques related to command and control communication and privilege escalation to ensure comprehensive defense against potential exploitation of this vulnerability.