CVE-2017-12623 in NiFi
Summary
by MITRE
An authorized user could upload a template which contained malicious code and accessed sensitive files via an XML External Entity (XXE) attack. The fix to properly handle XML External Entities was applied on the Apache NiFi 1.4.0 release. Users running a prior 1.x release should upgrade to the appropriate release.
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Analysis
by VulDB Data Team • 11/23/2019
The vulnerability identified as CVE-2017-12623 represents a critical security flaw in Apache NiFi versions prior to 1.4.0 that allows authenticated users to exploit XML External Entity processing weaknesses. This vulnerability specifically targets the template handling functionality within NiFi's web interface, creating a pathway for malicious code execution through carefully crafted template uploads. The issue stems from insufficient validation and sanitization of XML content, particularly when processing external entities that can reference local files or network resources.
The technical implementation of this vulnerability involves the manipulation of NiFi's template system where users with legitimate access privileges can upload custom templates containing malicious XML entities. When these templates are processed, the system fails to properly restrict external entity resolution, allowing attackers to reference local files through XXE mechanisms. This flaw enables unauthorized access to sensitive data and system resources that would normally be protected from direct file system access. The vulnerability operates at the application layer and specifically impacts NiFi's template processing capabilities, making it particularly dangerous in environments where template functionality is used for configuration management.
The operational impact of CVE-2017-12623 extends beyond simple data theft, as it can potentially enable attackers to escalate privileges and gain deeper system access. An authenticated attacker with template upload capabilities can leverage this vulnerability to read arbitrary files from the server's file system, potentially accessing configuration files, credentials, or other sensitive data stored locally. This represents a significant risk in enterprise environments where NiFi serves as a data flow management system handling sensitive information. The vulnerability can be exploited to bypass traditional access controls and gain unauthorized system access through the template upload mechanism.
Organizations using Apache NiFi versions prior to 1.4.0 should immediately implement the recommended mitigation by upgrading to the patched release that properly handles XML External Entities. The fix implemented in NiFi 1.4.0 addresses the core issue by implementing proper XML entity validation and disabling external entity resolution for template processing. This vulnerability aligns with CWE-611 (Improper Restriction of XML External Entity Reference) and can be mapped to ATT&CK technique T1059 (Command and Scripting Interpreter) through the execution of malicious code via template manipulation. Additionally, the vulnerability demonstrates characteristics of T1566 (Phishing) and T1078 (Valid Accounts) as it requires legitimate user credentials to exploit but can lead to privilege escalation and data exfiltration.
Security teams should implement additional monitoring for template upload activities and establish strict validation controls for XML content processing. The vulnerability highlights the importance of proper input validation and secure coding practices in web applications, particularly when handling user-supplied content that may be processed as structured data. Organizations should also consider implementing network segmentation and access controls to limit the potential impact of such vulnerabilities, as the ability to read local files through XXE attacks can provide attackers with significant information about the target system and its configuration.