CVE-2017-1000052 in Elixir Plug
Summary
by MITRE
Elixir Plug before v1.0.4, v1.1.7, v1.2.3 and v1.3.2 is vulnerable to null byte injection in the Plug.Static component, which may allow users to bypass filetype restrictions.
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Analysis
by VulDB Data Team • 10/26/2019
The vulnerability identified as CVE-2017-1000052 affects the Elixir Plug framework version prior to specific patches, specifically targeting the Plug.Static component that handles static file serving within web applications. This issue represents a critical security flaw that can be exploited to circumvent file type restrictions that are typically enforced by web applications to prevent access to sensitive files. The vulnerability manifests through improper handling of null byte characters in file paths, creating a potential attack vector that allows malicious users to manipulate file access controls and potentially gain unauthorized access to protected resources.
The technical root cause of this vulnerability lies in the insufficient sanitization of file paths within the Plug.Static module, where null byte injection attacks can be leveraged to manipulate how file paths are processed and validated. When a request contains a null byte character within the file path, the application may incorrectly interpret the path, effectively truncating the filename at the null byte position and allowing access to files that would normally be restricted. This behavior directly violates the fundamental security principle of proper input validation and demonstrates a classic case of improper handling of special characters in file system operations. The vulnerability is particularly dangerous because it can be exploited to bypass security measures that rely on file extension checks, potentially allowing attackers to access configuration files, source code, or other sensitive resources that should remain protected.
The operational impact of this vulnerability extends beyond simple file access bypass, as it can enable attackers to perform a range of malicious activities including information disclosure, privilege escalation, and potential system compromise. Attackers can exploit this weakness to access files that contain sensitive information such as database credentials, application secrets, or system configuration details that are typically protected by file type restrictions. The vulnerability affects multiple versions of the Elixir framework, indicating it was a widespread issue that required coordinated patching across different release branches. This type of vulnerability aligns with CWE-170, which specifically addresses improper handling of null bytes in input processing, and can be mapped to ATT&CK technique T1059.007 for command and scripting interpreter usage, as attackers may leverage such bypasses to execute malicious code or gain deeper system access.
Organizations utilizing Elixir applications that employ the Plug framework must immediately implement mitigations to address this vulnerability, including upgrading to patched versions of the framework where available. The recommended remediation strategy involves applying the specific patches released by the Elixir team for versions v1.0.4, v1.1.7, v1.2.3, and v1.3.2, which include proper null byte sanitization in the Plug.Static component. Additionally, defensive programming practices should be implemented to validate all file paths and inputs through robust sanitization routines that explicitly check for and reject null byte sequences. Network segmentation and additional access controls should be considered as layered defenses, particularly for applications that handle sensitive data or operate in high-security environments. Security monitoring should include detection of unusual file access patterns that might indicate exploitation attempts, and regular security audits should verify that all components of the application stack properly handle special characters in file paths. The vulnerability serves as a reminder of the critical importance of input validation and proper sanitization in web application security, particularly when dealing with file system operations that are fundamental to many web applications.