CVE-2026-84775 in Really Simple SSL Plugin
Summary
by MITRE • 09/02/2026
Unauthenticated Denial of Service Attack in Really Simple SSL <= 9.8.0 versions.
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Analysis
by VulDB Data Team • 09/02/2026
The vulnerability identified as an unauthenticated denial of service attack within the Really Simple SSL plugin, specifically affecting versions up to and including 9.8.0, represents a significant risk to web infrastructure integrity. This flaw allows any remote attacker who does not require valid credentials or authentication tokens to disrupt the availability of targeted WordPress websites. The core issue stems from insufficient input validation and resource management mechanisms within the plugin's codebase, which can be exploited through crafted HTTP requests that trigger excessive server-side processing or memory consumption without proper safeguards.
From a technical perspective, this vulnerability is classified under CWE-400, which denotes uncontrolled resource consumption leading to denial of service conditions. The attack vector typically involves sending specific malformed or excessively large payloads via standard web protocols such as HTTPS or HTTP. Because the plugin handles SSL certificate management and redirection logic, it may process these requests in a manner that consumes disproportionate amounts of CPU cycles or memory on the hosting server. This exploitation does not require prior access to the WordPress admin dashboard, making it particularly dangerous for sites with exposed administrative endpoints or those relying solely on default security configurations.
The operational impact of this vulnerability is primarily centered around service availability rather than data confidentiality or integrity. An attacker can leverage this flaw to cause temporary unresponsiveness or complete crashes of the web server hosting the vulnerable application. This results in a denial of service for legitimate users attempting to access the website, potentially leading to business disruption and loss of trust among visitors. In environments where high availability is critical, such as e-commerce platforms or corporate intranets, even brief periods of downtime can have substantial financial and reputational consequences. The lack of authentication requirements means that automated scanning tools and malicious actors can easily identify and exploit this weakness across the internet at scale.
In terms of industry frameworks, this vulnerability aligns with MITRE ATT&CK technique T1498, Network Denial of Service, specifically sub-technique T1498.003 which involves application layer attacks that consume resources to degrade performance or cause outages. It also relates to CWE-770, Allocation of Resources Without Limits or Throttling, highlighting the failure to implement rate limiting or input size constraints effectively within the plugin's processing logic. Understanding these classifications helps security teams prioritize remediation efforts based on standardized risk assessment models rather than relying solely on vendor advisories.
Mitigation strategies for this vulnerability focus primarily on immediate patching and defensive configuration adjustments. The most effective solution is to upgrade the Really Simple SSL plugin to a version newer than 9.8.0, where the developers have presumably addressed the resource management flaws through code optimization and stricter input validation. Organizations should verify their current plugin versions regularly using automated inventory tools integrated into their vulnerability management workflows. Additionally, implementing web application firewalls can provide an additional layer of defense by detecting and blocking anomalous traffic patterns associated with denial of service attempts before they reach the vulnerable application logic.
Administrators should also consider enabling rate limiting on their web servers to mitigate the impact of such attacks if patching cannot be performed immediately. Configuring server-side limits for request rates per IP address can help absorb or deflect automated exploitation attempts. Furthermore, monitoring server resource usage metrics such as CPU and memory utilization during peak traffic periods can aid in early detection of potential abuse. Regular security audits and penetration testing that include unauthenticated attack scenarios are recommended to ensure that similar vulnerabilities do not exist elsewhere in the application stack. Maintaining up-to-date software components remains the most critical defense against evolving threats targeting widely used plugins like Really Simple SSL.