CVE-2007-0539 in WordPress
Summary
by MITRE
The wp_remote_fopen function in WordPress before 2.1 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 large file, which triggers a long download session without a timeout constraint.
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Analysis
by VulDB Data Team • 08/18/2018
The vulnerability identified as CVE-2007-0539 represents a significant denial of service weakness in WordPress versions prior to 2.1, specifically within the wp_remote_fopen function that handles remote file operations. This flaw enables remote attackers to exploit the pingback service functionality by providing a source URI that points to a large file, thereby initiating extended download sessions that lack proper timeout mechanisms. The technical implementation of this vulnerability stems from the absence of bandwidth or time constraints during remote file retrieval operations, creating an opportunity for malicious actors to consume excessive system resources. The pingback service in WordPress is designed to notify other blogs when a link is made to them, but this functionality becomes a vector for resource exhaustion when improperly validated.
The operational impact of this vulnerability extends beyond simple service disruption to encompass substantial resource consumption that can affect system performance and availability. Attackers can leverage this weakness by crafting pingback requests that reference large files such as video content or large binary files, causing WordPress to initiate lengthy download processes that consume network bandwidth and system threads. This resource exhaustion can lead to denial of service conditions where legitimate users experience degraded performance or complete service unavailability. The vulnerability particularly affects systems with limited bandwidth or processing capabilities, making it a serious concern for web hosts and content management systems running vulnerable WordPress installations. The lack of timeout constraints means that downloads can persist indefinitely, potentially exhausting server resources and creating cascading effects that impact other services running on the same infrastructure.
Security practitioners should recognize this vulnerability as a classic example of improper resource management and inadequate input validation, aligning with CWE-400 which addresses "Uncontrolled Resource Consumption" and CWE-20 which covers "Improper Input Validation." The attack vector follows patterns consistent with the ATT&CK framework's privilege escalation and denial of service techniques, where adversaries leverage application-level weaknesses to consume system resources. Organizations should implement immediate mitigations including updating to WordPress 2.1 or later versions that address this specific vulnerability, configuring proper timeout values for remote file operations, and implementing rate limiting for pingback service calls. Additional defensive measures include monitoring network traffic for unusual patterns of large file downloads, implementing firewall rules to restrict access to pingback endpoints, and establishing proper resource quotas for concurrent download operations. The vulnerability underscores the importance of proper timeout mechanisms in remote service calls and demonstrates how seemingly benign functionality can become a security risk when proper resource management practices are not implemented.