CVE-2019-15596 in statics-server
Summary
by MITRE
A path traversal in statics-server exists in all version that allows an attacker to perform a path traversal when a symlink is used within the working directory.
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Analysis
by VulDB Data Team • 03/15/2024
The vulnerability identified as CVE-2019-15596 represents a critical path traversal flaw within statics-server software across all affected versions. This security weakness specifically manifests when symbolic links are present within the working directory of the server, creating an exploitable condition that allows unauthorized access to files outside the intended document root. The vulnerability stems from inadequate input validation and path resolution mechanisms that fail to properly sanitize or restrict file access when symbolic links are encountered during static file serving operations. Attackers can leverage this flaw to traverse the file system hierarchy and potentially access sensitive files, configuration data, or system resources that should remain isolated from web access. The issue is particularly concerning because it operates at the core of static file serving functionality, which is fundamental to web server operations and typically handles user requests for static content such as images, CSS files, JavaScript assets, and other non-executable resources.
The technical implementation of this vulnerability occurs through the improper handling of symbolic links within the server's file resolution process. When a maliciously crafted request contains path traversal sequences combined with existing symbolic links in the working directory, the server fails to properly validate the resulting path before serving content. This allows attackers to craft URLs that, when processed, resolve to arbitrary file locations on the server's file system. The flaw is classified as a path traversal vulnerability under CWE-22, which specifically addresses improper limitation of a pathname to a restricted directory, commonly known as directory traversal attacks. The vulnerability operates at the file system level where the server's static file serving component does not adequately canonicalize or validate file paths, particularly when symbolic links are involved in the resolution process. This weakness creates a direct pathway for attackers to bypass normal access controls and potentially gain unauthorized access to sensitive data, including system configuration files, user data, or application secrets stored outside the intended web root directory.
The operational impact of CVE-2019-15596 extends beyond simple unauthorized file access, as it can enable attackers to escalate their privileges and potentially compromise the entire server infrastructure. An attacker who successfully exploits this vulnerability can access sensitive files such as database credentials, application configuration files, or system user data that may contain authentication tokens, private keys, or other critical information. The vulnerability is particularly dangerous in environments where statics-server is used to serve content from directories that contain symbolic links pointing to system directories or other sensitive locations. This flaw can be exploited by attackers to gain access to system-level information, potentially leading to further exploitation opportunities such as privilege escalation or lateral movement within the network. The vulnerability also poses risks to data confidentiality and integrity, as attackers can not only read sensitive files but may also potentially modify or delete files if the server has write permissions to the affected directories. According to ATT&CK framework, this vulnerability maps to T1083 (File and Directory Discovery) and T1566 (Phishing with Malicious Attachment) where attackers can use the path traversal to discover and exfiltrate sensitive data from the system.
Mitigation strategies for CVE-2019-15596 should focus on both immediate defensive measures and long-term architectural improvements. Organizations should immediately update to patched versions of statics-server where available, as this vulnerability is likely to have been addressed through proper path validation and canonicalization mechanisms. When updates are not immediately possible, administrators should implement strict file system permissions that prevent the creation of symbolic links in directories serving static content, or alternatively, disable symbolic link resolution entirely within the server configuration. Additionally, input validation should be implemented at the application level to sanitize all file paths and reject requests containing suspicious path traversal sequences such as double dots or backslashes. Network-level mitigations can include implementing web application firewalls that can detect and block known path traversal patterns in HTTP requests. Security monitoring should be enhanced to detect unusual file access patterns or attempts to access system directories through static file serving endpoints. The implementation of principle of least privilege should be enforced, ensuring that the statics-server process runs with minimal required permissions and cannot access directories outside the intended serving scope. Regular security audits and penetration testing should be conducted to identify and remediate similar vulnerabilities in other components of the web infrastructure, as this type of path traversal vulnerability often indicates broader security gaps in file system access controls and input validation mechanisms.