Description

Unauthenticated Denial of Service Attack in Really Simple SSL <= 9.8.0 versions.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "5.3",
  "pubDate": "2026-09-02T12:17:15.293Z",
  "pubdate": "2026-09-02T12:17:15.293Z",
  "executiveSummary": "This vulnerability involves an unauthenticated Denial of Service (DoS) flaw within the Really Simple SSL plugin, specifically affecting versions 9.8.0 and earlier.\nThe vulnerability allows an unauthenticated remote attacker to trigger a service disruption by sending specially crafted requests to the target system.\nThe primary risk implication is the degradation or complete loss of service availability for the affected WordPress installation, which can be achieved without requiring administrative privileges or user authentication.\nAs an unauthenticated attack vector, this vulnerability can be leveraged by any actor with network access to the target web server, requiring no prior knowledge of site credentials.\nThe flaw stems from improper input handling or resource management within the plugin, leading to excessive consumption of server resources or application crashes when processing malicious payloads.\nGiven the ubiquitous nature of such plugins, successful exploitation poses a significant operational threat, potentially causing site-wide outages, performance degradation, and administrative lockouts.\nOrganizations utilizing affected versions of Really Simple SSL are exposed to service disruption until the vulnerability is addressed.",
  "technicalDetails": "The vulnerability exists within the Really Simple SSL plugin versions <= 9.8.0, stemming from a lack of sufficient input validation or resource throttling during the handling of specific unauthenticated requests.\nThe root cause is identified as an improper implementation of request processing logic, which allows an attacker to manipulate parameters or request headers in a way that forces the application into an infinite loop, excessive memory allocation, or excessive database/disk I/O operations.\nBecause the vulnerable functionality is exposed to the public internet without requiring authentication, an attacker can initiate the exploitation process by sending a single malicious HTTP request or a series of requests to the site’s public-facing endpoints.\nThe attack flow follows a predictable pattern: 1) The attacker identifies the vulnerable plugin version through reconnaissance or blind enumeration; 2) The attacker crafts a request containing the specific malicious payload that triggers the flawed code path; 3) The server attempts to process this request, resulting in the exhaustion of CPU, memory, or database connection pools; 4) The service becomes unresponsive to legitimate user traffic, resulting in a complete Denial of Service.\nUnlike vulnerabilities that require specific elevated privileges, this flaw bypasses standard security barriers by exploiting the plugin's interaction with the core WordPress environment before the application layer can perform robust access control checks.\nThe payload behavior is designed to maximize resource contention. If the plugin fails to sanitize input correctly, it may allow for complex recursive calls or object instantiation that exceeds PHP execution limits or memory thresholds (e.g., memory_limit).\nPost-exploitation impact is limited to service availability. The attacker does not necessarily gain unauthorized access to data or code execution capabilities, but the inability to serve requests effectively disables the target system.\nThe vulnerable component likely resides in the plugin's core request interception logic or its custom authentication hooks, which are executed during the initial bootstrapping phase of the WordPress request lifecycle. Consequently, the mitigation of this issue requires a fundamental change in how the plugin handles unauthenticated input to prevent resource depletion."
}