CVE-2016-5836 in WordPress
Summary
by MITRE
The oEmbed protocol implementation in WordPress before 4.5.3 allows remote attackers to cause a denial of service via unspecified vectors.
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Analysis
by VulDB Data Team • 05/08/2019
The vulnerability identified as CVE-2016-5836 represents a significant denial of service weakness within WordPress's oEmbed protocol implementation that affected versions prior to 4.5.3. This flaw resides in how WordPress processes oEmbed requests, which are designed to allow embedding of content from external sources such as videos, images, and other media types into blog posts and pages. The oEmbed protocol serves as a standardized method for embedding third-party content, enabling users to paste URLs and have WordPress automatically generate appropriate embed codes. However, the implementation contained a critical design oversight that could be exploited by remote attackers to disrupt normal service operations.
The technical nature of this vulnerability stems from insufficient input validation and sanitization within the oEmbed processing pipeline. Attackers could craft malicious oEmbed requests that would cause WordPress to consume excessive system resources or enter into infinite loops during the processing of these requests. This weakness allowed for a variety of attack vectors that could overwhelm server resources, leading to service unavailability for legitimate users. The unspecified nature of the vectors suggests that multiple approaches could be employed to trigger the denial of service condition, making the vulnerability particularly concerning as it could be exploited through various means without requiring specific knowledge of the exact triggering mechanism.
The operational impact of CVE-2016-5836 extends beyond simple service disruption to potentially affect the entire WordPress ecosystem. When exploited, this vulnerability could render WordPress sites inaccessible to visitors, causing significant business disruption for websites that rely heavily on their content management system. The attack could be executed remotely without requiring authentication, making it particularly dangerous as it could be exploited by anyone with knowledge of the target WordPress installation. Organizations running vulnerable versions would experience cascading effects including potential loss of revenue, decreased user engagement, and damage to brand reputation. The vulnerability also poses risks to hosting providers who may experience resource exhaustion across multiple client sites simultaneously.
Security professionals should recognize this vulnerability as aligning with CWE-400, which addresses "Uncontrolled Resource Consumption," and can be mapped to ATT&CK technique T1499.004 for "Utilities: Service Stop." The remediation strategy centers on upgrading to WordPress version 4.5.3 or later, which includes patches that address the resource consumption issues in the oEmbed implementation. Additionally, administrators should implement rate limiting mechanisms to prevent abuse of oEmbed functionality, configure proper input validation for external URL processing, and consider implementing network-level controls to monitor and restrict oEmbed requests from suspicious sources. Organizations should also conduct regular security assessments to identify and remediate similar vulnerabilities in their WordPress installations, as this type of resource exhaustion attack represents a common vector for disrupting web services and can be effectively mitigated through proper configuration and timely patch management.