CVE-2007-0540 in WordPress
Summary
by MITRE
WordPress allows remote attackers to cause a denial of service (bandwidth or thread consumption) via pingback service calls with a source URI that corresponds to a file with a binary content type, which is downloaded even though it cannot contain usable pingback data.
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Analysis
by VulDB Data Team • 08/10/2019
The vulnerability described in CVE-2007-0540 represents a significant denial of service weakness within WordPress installations that stems from improper handling of pingback service requests. This flaw specifically targets the pingback functionality that WordPress implements to notify other websites when they link to content on a WordPress site. The vulnerability exists in how WordPress processes incoming pingback requests, particularly when the source URI points to files with binary content types such as executables, images, or other non-textual data formats.
The technical mechanism behind this vulnerability involves the pingback service attempting to download and process content from remote URIs to extract potential pingback data. When a malicious actor sends a pingback request pointing to a file with binary content, WordPress will still attempt to download the entire file regardless of its content type. This behavior creates a resource exhaustion scenario where the web server consumes significant bandwidth and processing threads while downloading potentially large binary files that contain no usable pingback information. The flaw operates at the application layer and can be exploited through the XML-RPC interface that WordPress uses for pingback operations.
From an operational impact perspective, this vulnerability allows remote attackers to consume excessive system resources including network bandwidth, server processing power, and memory allocation. The denial of service occurs gradually as the server threads become occupied with downloading binary content that cannot be parsed for pingback data. This can lead to legitimate users experiencing slower service or complete unavailability of the WordPress site, particularly affecting smaller installations with limited bandwidth or processing capabilities. The vulnerability is particularly dangerous because it can be exploited without authentication and can be amplified through automated tools that send multiple concurrent pingback requests.
The weakness manifests as a failure to properly validate and filter incoming pingback requests based on content type and size constraints, which aligns with CWE-400, specifically related to resource exhaustion vulnerabilities. This vulnerability also maps to ATT&CK technique T1499.001, which describes resource exhaustion attacks targeting availability. The attack vector operates through the XML-RPC protocol that WordPress uses for various administrative functions, making it accessible to anyone who can submit pingback requests to the target system. The vulnerability demonstrates poor input validation and resource management practices in the WordPress core codebase, particularly in the pingback handling module.
Mitigation strategies should focus on implementing strict content type validation for pingback requests, establishing size limits for downloaded content, and configuring rate limiting for pingback operations. Administrators should disable pingback functionality if it is not required for their specific use case, as outlined in WordPress security best practices. Network-level controls such as firewall rules that restrict access to XML-RPC endpoints can provide additional protection. The most effective long-term solution involves patching the WordPress core to implement proper content validation and resource limiting mechanisms. Security monitoring should include detection of unusual pingback traffic patterns and excessive bandwidth consumption that may indicate exploitation attempts.