CVE-2017-17663 in mini_httpd
Summary
by MITRE
The htpasswd implementation of mini_httpd before v1.28 and of thttpd before v2.28 is affected by a buffer overflow that can be exploited remotely to perform code execution.
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Analysis
by VulDB Data Team • 01/02/2020
The vulnerability identified as CVE-2017-17663 represents a critical buffer overflow flaw affecting two widely deployed HTTP server implementations mini_httpd and thttpd. This vulnerability resides within the htpasswd authentication handling mechanism of these web servers, creating a remote code execution vector that can be exploited by malicious actors without authentication. The affected versions include mini_httpd prior to v1.28 and thttpd prior to v2.28, indicating that this flaw has persisted for several years within the software ecosystem. The buffer overflow occurs during the processing of authentication credentials, specifically when handling user credentials provided through htpasswd files, making it a fundamental security weakness in the authentication subsystem of these lightweight web servers.
The technical nature of this vulnerability stems from improper bounds checking within the string handling functions used by the htpasswd implementation. When the web server processes authentication requests, it fails to validate the length of input data before copying it into fixed-size buffers, creating an exploitable condition where malicious input can overwrite adjacent memory locations. This memory corruption can be leveraged to overwrite return addresses, function pointers, or other critical program state information, enabling attackers to redirect program execution flow. The vulnerability manifests when the server receives specially crafted authentication requests that exceed the allocated buffer space, causing stack-based buffer overflow conditions that are particularly dangerous in server applications where code execution privileges are elevated. According to CWE standards, this corresponds to CWE-121, which describes stack-based buffer overflow conditions, and the vulnerability aligns with ATT&CK technique T1203 for exploitation of remote services.
The operational impact of CVE-2017-17663 extends beyond simple privilege escalation as it enables full remote code execution capabilities against affected systems. Attackers can leverage this vulnerability to gain complete control over the web server process, potentially leading to unauthorized access to sensitive data, system compromise, or use of the compromised server as a pivot point for further attacks within the network. The vulnerability is particularly concerning because these web servers are commonly deployed in embedded systems, network appliances, and legacy environments where patching may be infrequent or impossible, creating extended attack windows. The remote exploitation capability means that attackers can target these systems from anywhere on the network without requiring physical access or local credentials, making the vulnerability highly attractive for automated attack campaigns.
Mitigation strategies for this vulnerability must prioritize immediate patching of affected systems, with administrators updating to mini_httpd v1.28 or thttpd v2.28 releases that contain the necessary security fixes. Network segmentation and firewall rules should be implemented to limit access to these web servers, particularly restricting access to authentication endpoints and administrative interfaces. Additional protective measures include implementing intrusion detection systems to monitor for exploitation attempts, disabling unnecessary authentication mechanisms when possible, and conducting comprehensive vulnerability assessments to identify other potentially affected services. Organizations should also consider implementing application-level firewalls or web application firewalls to filter malicious authentication requests before they reach the vulnerable components. The vulnerability demonstrates the importance of proper input validation and memory safety practices in server software development, aligning with security best practices outlined in various industry standards including OWASP Top Ten and NIST cybersecurity guidelines. Regular security audits and penetration testing should be conducted to identify similar buffer overflow vulnerabilities in other network services and applications.