CVE-2013-0235 in WordPress
Summary
by MITRE
The XMLRPC API in WordPress before 3.5.1 allows remote attackers to send HTTP requests to intranet servers, and conduct port-scanning attacks, by specifying a crafted source URL for a pingback, related to a Server-Side Request Forgery (SSRF) issue.
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Analysis
by VulDB Data Team • 04/22/2021
The vulnerability identified as CVE-2013-0235 represents a critical server-side request forgery flaw in WordPress versions prior to 3.5.1, specifically within the XMLRPC API implementation. This vulnerability enables remote attackers to manipulate the pingback functionality to initiate HTTP requests to internal network resources, effectively bypassing standard network security controls that typically protect internal systems from external access. The flaw resides in how WordPress processes pingback requests through its XMLRPC interface, where the system fails to properly validate or sanitize the source URL parameter provided by external parties. This allows malicious actors to craft specially formatted pingback requests that instruct the WordPress server to make HTTP connections to arbitrary internal IP addresses or domains, exploiting the trust relationship between the WordPress server and internal network resources.
The technical implementation of this vulnerability leverages the pingback feature designed for legitimate web content synchronization, where WordPress typically verifies links between websites by making HTTP requests to the source URL to confirm the existence of a link. However, the XMLRPC API in vulnerable versions does not adequately restrict the URLs that can be specified in pingback requests, allowing attackers to specify internal network addresses such as private IP ranges or localhost addresses. This creates a pathway for attackers to perform port scanning activities against internal network infrastructure, as the WordPress server will attempt to connect to the specified URLs and return results based on whether the connections succeed or fail. The vulnerability is particularly dangerous because it can be exploited without authentication, making it accessible to anyone who can submit pingback requests to a vulnerable WordPress installation.
The operational impact of CVE-2013-0235 extends beyond simple port scanning capabilities, as it provides attackers with a method to map internal network topology and identify potentially vulnerable internal services. Network administrators may discover that their internal systems are being probed by external entities through the WordPress server, creating a stealthy reconnaissance mechanism that bypasses traditional firewall rules and network segmentation controls. This vulnerability directly aligns with the Common Weakness Enumeration CWE-918, which classifies server-side request forgery issues where applications fail to properly validate or restrict external resource access. The attack vector maps to the MITRE ATT&CK framework's technique T1133, which describes external remote services and T1071, which covers application layer protocol usage, specifically highlighting how attackers can leverage legitimate application features for malicious purposes.
Organizations running vulnerable WordPress installations face significant risks including unauthorized network reconnaissance, potential exploitation of internal services, and the possibility of lateral movement within their network infrastructure. The vulnerability can be exploited by attackers to identify open ports, discover running services, and potentially uncover vulnerable internal systems that might not be directly exposed to the internet. Security teams should implement immediate mitigation strategies including updating WordPress installations to version 3.5.1 or later, where the vulnerability has been patched through proper URL validation in the XMLRPC API. Additional protective measures include configuring firewall rules to restrict outbound connections from WordPress servers, implementing network segmentation to limit access to internal resources, and monitoring for unusual pingback activity that may indicate exploitation attempts. The patch for this vulnerability specifically addresses the lack of input validation in the pingback URL parameter, ensuring that only properly formatted and externally accessible URLs are processed by the XMLRPC API, thereby preventing the exploitation of the server-side request forgery mechanism.