CVE-2018-18778 in mini_httpd
Summary
by MITRE
ACME mini_httpd before 1.30 lets remote users read arbitrary files.
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Analysis
by VulDB Data Team • 04/07/2020
The CVE-2018-18778 vulnerability affects ACME mini_httpd versions prior to 1.30, representing a critical directory traversal flaw that enables remote attackers to access arbitrary files on the affected system. This vulnerability stems from insufficient input validation within the web server's file handling mechanisms, allowing malicious users to manipulate request parameters to bypass normal file access controls. The flaw specifically manifests when the application processes HTTP requests containing crafted path traversal sequences that can navigate beyond the intended document root directory. Security researchers identified that the vulnerability operates through the manipulation of directory path components in HTTP requests, enabling attackers to retrieve files that should remain inaccessible to unauthorized users.
The technical implementation of this vulnerability exploits the absence of proper sanitization for file path parameters within the mini_httpd web server implementation. When processing HTTP requests, the server fails to adequately validate or normalize file paths, allowing attackers to append sequences such as ../ or ..\ to navigate through the file system hierarchy. This weakness directly maps to CWE-22, which defines improper limitation of a pathname to a restricted directory, commonly known as directory traversal or path traversal attacks. The vulnerability can be leveraged by remote unauthenticated attackers who do not require any special privileges to exploit the flaw, making it particularly dangerous in publicly accessible web server environments. The impact extends beyond simple file reading, as attackers can potentially access sensitive configuration files, authentication credentials, or system files that contain confidential information.
The operational impact of CVE-2018-18778 is severe and multifaceted, as it can lead to complete system compromise when combined with other attack vectors. Attackers can utilize this vulnerability to read sensitive system files including password hashes, configuration files containing database credentials, or application source code that may reveal additional vulnerabilities. The attack surface is particularly broad since mini_httpd is commonly used in embedded systems, network appliances, and IoT devices where security controls may be minimal. According to ATT&CK framework tactics, this vulnerability aligns with T1083 (File and Directory Discovery) and T1566 (Phishing with Malicious Attachments) as attackers can discover and exfiltrate sensitive data. Organizations running vulnerable versions face potential data breaches, regulatory compliance violations, and reputational damage when attackers successfully exploit this flaw to access confidential information.
Mitigation strategies for CVE-2018-18778 primarily focus on immediate software updates and implementation of additional security controls. The most effective remediation involves upgrading to ACME mini_httpd version 1.30 or later, which includes proper input validation and path normalization mechanisms that prevent directory traversal attempts. Organizations should also implement web application firewalls or security proxies that can detect and block malicious path traversal patterns in HTTP requests. Additional defensive measures include restricting file system permissions for web server processes, implementing proper access controls, and conducting regular security audits of web server configurations. Network segmentation and monitoring solutions should be deployed to detect anomalous file access patterns that may indicate exploitation attempts. The vulnerability demonstrates the critical importance of input validation in web server implementations and highlights the necessity of following secure coding practices that prevent common attack patterns such as those defined in the OWASP Top Ten project. Organizations should also consider implementing automated vulnerability scanning tools that can identify similar path traversal vulnerabilities in other web applications and services.