CVE-2018-19630 in OpenWrt
Summary
by MITRE
cgi_handle_request in uhttpd in OpenWrt through 18.06.1 and LEDE through 17.01 has unauthenticated reflected XSS via the URI, as demonstrated by a cgi-bin/?[XSS] URI.
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Analysis
by VulDB Data Team • 04/16/2020
The vulnerability identified as CVE-2018-19630 represents a critical unauthenticated reflected cross-site scripting flaw in the uhttpd web server component of OpenWrt and LEDE operating systems. This vulnerability specifically affects versions through 18.06.1 for OpenWrt and 17.01 for LEDE, where the cgi_handle_request function fails to properly sanitize user-supplied input from URI parameters. The flaw manifests when a maliciously crafted URI containing XSS payload is submitted to the cgi-bin endpoint, allowing an attacker to inject malicious scripts that execute in the context of authenticated users' browsers. The vulnerability resides in the web server's handling of request parameters without adequate input validation or output encoding, creating a persistent security risk for devices running these firmware versions.
The technical implementation of this vulnerability stems from improper input sanitization within the uhttpd web server's CGI request handling mechanism. When a URI containing reflected XSS payloads is processed by the cgi_handle_request function, the system fails to properly escape or validate the input parameters before incorporating them into HTTP responses. This allows an attacker to craft malicious URIs such as cgi-bin/?<script>alert(1)</script> which, when visited by a victim, will execute the injected script in the victim's browser context. The vulnerability is classified as reflected XSS because the malicious payload is reflected back to the user through the web server's response without any server-side processing or storage of the input. This type of vulnerability directly maps to CWE-79 which defines Cross-Site Scripting as a weakness where untrusted data is sent to a web browser without proper validation or encoding.
The operational impact of CVE-2018-19630 extends beyond simple script execution, as it can enable attackers to perform various malicious activities including session hijacking, credential theft, and redirection to malicious websites. An attacker could leverage this vulnerability to steal authentication cookies from authenticated users, potentially gaining unauthorized access to router administration interfaces. The unauthenticated nature of this flaw means that any user with access to the network can exploit it without requiring prior authentication credentials, making it particularly dangerous in network environments where router management interfaces are accessible from external networks. Additionally, the vulnerability could be combined with other attack vectors to create more sophisticated exploitation chains, potentially leading to complete network compromise and persistent backdoor access. This weakness aligns with ATT&CK technique T1212 which describes exploitation of software vulnerabilities to gain access to systems, and T1071.004 which covers application layer protocol manipulation through web application attacks.
Mitigation strategies for CVE-2018-19630 should prioritize immediate firmware updates to versions that have patched the vulnerability, as this represents the most effective and comprehensive solution. Network administrators should also implement proper input validation at the network perimeter through web application firewalls or intrusion prevention systems that can detect and block malicious URI patterns. Additional protective measures include restricting access to router management interfaces to trusted IP ranges only, disabling unnecessary CGI functionality when not required, and implementing proper output encoding for all web server responses. Organizations should also consider network segmentation to limit the potential impact of successful exploitation and establish monitoring procedures to detect unusual traffic patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of input validation in web applications and highlights the need for comprehensive security testing of embedded systems, particularly those handling user input through web interfaces.