CVE-2026-39767 in Cache Plugin
Summary
by MITRE • 10/06/2026
Subscriber Denial of Service Attack in WPBase Cache <= 5.5.6 versions.
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Analysis
by VulDB Data Team • 10/06/2026
The vulnerability identified as a Subscriber Denial of Service attack within the WPBase Cache plugin, specifically affecting versions up to and including 5.5.6, represents a significant security risk for WordPress-based websites that rely on this caching mechanism for performance optimization. This flaw stems from an insufficient validation or rate-limiting implementation in the administrative interface or API endpoints exposed by the plugin, allowing users with low-privilege accounts, such as subscribers, to trigger resource-intensive operations without adequate restrictions. In a typical web application architecture, subscriber-level access is intended to be read-only or limited to basic profile management, yet this vulnerability subverts those expectations by enabling these lower-tier actors to execute actions that consume substantial server resources, thereby degrading the availability of the entire website for all users regardless of their authentication status.
From a technical perspective, the core issue lies in the lack of proper authorization checks and input sanitization when handling cache-related requests initiated by authenticated subscribers. The plugin likely fails to verify whether the user initiating a flush, purge, or regeneration request possesses the necessary administrative privileges before proceeding with the operation. When such operations are triggered repeatedly or through automated scripts, they can exhaust server memory, CPU cycles, or database connections, leading to service degradation or complete unavailability of the web application. This type of flaw is commonly categorized under CWE-269 Improper Privilege Management and CWE-770 Allocation of Resources Without Limits or Throttling, as it allows an actor with limited privileges to perform actions that should be restricted to higher-level administrators while simultaneously failing to limit resource consumption per request or user session.
The operational impact of this vulnerability is primarily centered on availability rather than confidentiality or integrity. Attackers can exploit this flaw to conduct a Denial of Service attack, effectively rendering the website inaccessible to legitimate visitors by overwhelming server resources with maliciously crafted requests. This not only disrupts business operations and user experience but also increases hosting costs due to excessive resource consumption during prolonged attacks. Furthermore, because WordPress is one of the most widely used content management systems globally, a successful exploitation can have cascading effects on downstream services that depend on the availability of these websites for data ingestion or integration purposes. The ease with which this attack can be automated makes it particularly dangerous in large-scale environments where multiple sites may be targeted simultaneously to amplify the impact.
Mitigation strategies must focus on immediate remediation and long-term defensive measures. Administrators should update the WPBase Cache plugin to version 5.5.7 or later, where these privilege checks have been corrected to ensure that only users with appropriate administrative roles can trigger cache-clearing operations. In cases where updating is not immediately feasible, temporary workarounds include restricting access to the WordPress admin area via IP whitelisting for all non-administrative user accounts and implementing web application firewall rules that detect and block excessive requests from subscriber-level sessions targeting caching endpoints. Additionally, enforcing strict rate limiting on API calls related to cache management can help mitigate the impact of such attacks by throttling resource-intensive operations before they cause significant system strain.
Long-term resilience against similar vulnerabilities requires adherence to secure coding practices emphasized in industry standards such as OWASP Top 10 and NIST guidelines for web application security. Developers must implement robust role-based access control mechanisms that strictly enforce privilege boundaries, ensuring that actions are validated not only by user identity but also by their assigned roles within the system context. Input validation should be applied consistently to all parameters passed through API endpoints or form submissions, regardless of the perceived trustworthiness of the source. Regular security audits and penetration testing focused on authorization bypasses can help identify such flaws before they are exploited in production environments. By integrating these practices into the development lifecycle, organizations can significantly reduce their attack surface and maintain high availability standards for their web applications.