CVE-2007-0541 in WordPress
Summary
by MITRE
WordPress allows remote attackers to determine the existence of arbitrary files, and possibly read portions of certain files, via pingback service calls with a source URI that corresponds to a local pathname, which triggers different fault codes for existing and non-existing files, and in certain configurations causes a brief file excerpt to be published as a blog comment.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 07/14/2019
This vulnerability in WordPress represents a significant information disclosure flaw that enables remote attackers to enumerate local file system contents through the pingback service functionality. The vulnerability specifically affects WordPress versions prior to 2.1.1 and stems from improper validation of source URIs in pingback requests. When attackers submit pingback service calls with source URIs pointing to local file paths, the system responds with different error codes depending on whether the specified file exists or not. This differential response behavior creates a side-channel attack vector that allows adversaries to determine the existence of arbitrary files on the server filesystem. The vulnerability is particularly dangerous because it can be exploited without authentication, making it accessible to any remote attacker with knowledge of the target WordPress installation. The flaw operates at the application level and demonstrates poor input validation practices in the pingback implementation, which is designed to handle external web references for blog post linking and notification purposes.
The technical mechanism behind this vulnerability involves the pingback service's handling of malformed or malicious source URIs. When WordPress processes a pingback request, it attempts to resolve the source URI and validate the referenced content. In vulnerable versions, the system does not properly sanitize or validate these URIs before processing them, allowing local file path references to be interpreted as valid inputs. The system's response varies based on file existence - existing files generate one type of error code while non-existing files generate another, creating a clear distinction that can be exploited through systematic testing. In certain server configurations, the vulnerability can escalate beyond simple file existence enumeration to potentially exposing partial file contents through blog comments. This occurs because the pingback service may inadvertently include portions of the referenced file in its error responses or comment publication, effectively leaking sensitive data from the server's file system.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with valuable reconnaissance data for subsequent attacks. Successful exploitation allows adversaries to map the target server's file structure, potentially identifying sensitive files such as configuration files, database credentials, or application source code. The vulnerability can be leveraged as a stepping stone for more sophisticated attacks, including privilege escalation, remote code execution, or further system compromise. Attackers can systematically probe the file system to identify the presence of backup files, log files, or other sensitive resources that may contain useful information for exploitation. The vulnerability also demonstrates the broader security implications of improper input validation in web applications, where seemingly benign functionality can become a vector for serious security breaches. This flaw particularly affects WordPress installations that have pingback services enabled, which is the default configuration in many deployments.
Mitigation strategies for this vulnerability involve immediate patching of affected WordPress installations to version 2.1.1 or later, which contains the necessary fixes for the pingback service validation. Administrators should also disable pingback functionality if it is not required for their specific use case, as this eliminates the attack surface entirely. Additional protective measures include implementing proper input validation and sanitization for all URI inputs, restricting file system access through proper permissions, and monitoring for unusual pingback activity patterns. The vulnerability aligns with CWE-20 Improper Input Validation and CWE-352 Cross-Site Request Forgery categories, representing a classic example of how insufficient validation can lead to information disclosure. From an attack framework perspective, this vulnerability maps to the reconnaissance phase of the ATT&CK methodology, where adversaries gather information about target systems to inform subsequent exploitation efforts. Organizations should also consider implementing web application firewalls to detect and block suspicious pingback requests, and conduct regular security assessments to identify similar validation flaws in other application components.