CVE-2026-88798 in Really Simple Security Plugin
Summary
by MITRE • 09/18/2026
The Really Simple Security WordPress plugin before 9.8.3 does not validate a client-supplied address value before using it as a storage key in one of its own options, allowing unauthenticated attackers to grow that option without bound and to slow the site's handling of missing pages.
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Analysis
by VulDB Data Team • 09/18/2026
The Really Simple Security plugin for WordPress contains an input validation flaw within versions prior to 9.8.3 that allows unauthenticated actors to manipulate internal configuration storage mechanisms. The vulnerability stems from a failure to sanitize or validate client-supplied address values before they are utilized as keys in the plugin's options array. In typical web application architecture, user-provided data must be rigorously validated against expected formats and constraints before being used for critical operations such as database writes or memory allocation. By accepting arbitrary input without verification, the software exposes a mechanism that can be abused to inject excessive amounts of data into persistent storage structures managed by the plugin.
This lack of validation directly facilitates an unbounded resource consumption scenario. An attacker can repeatedly submit requests containing varying address values, each of which is stored as a new key in the options table without any limit on quantity or size. This behavior leads to the continuous growth of the database option entry associated with the plugin. As this storage structure expands indefinitely due to malicious input, it consumes increasing amounts of disk space and memory resources allocated for reading and processing these configuration values during routine site operations.
The operational impact of this vulnerability is primarily characterized by performance degradation rather than immediate data exfiltration or remote code execution. The most significant consequence manifests when the WordPress installation attempts to handle requests for missing pages, commonly known as 404 errors. During such events, the system must process various hooks and filters associated with security plugins to determine how to respond to the non-existent resource. Because the Really Simple Security plugin has accumulated a massive number of invalid or maliciously injected keys in its options array due to this flaw, the processing time required to iterate through these entries increases substantially. This results in noticeable latency for users attempting to access pages that do not exist on the site, effectively degrading the user experience and potentially causing timeouts under high load conditions.
From a classification perspective, this vulnerability aligns with CWE-787: Out-of-bounds Write or CWE-20: Improper Input Validation, as it involves accepting unchecked data that leads to unintended system state changes. In terms of attack vectors, the exploitation technique corresponds to ATT&CK T1496: Resource Hijacking, where an adversary uses computing resources for their own benefit by causing excessive resource consumption on a target system. While not typically classified as a critical severity vulnerability due to its denial-of-service nature rather than direct compromise, it represents a significant reliability risk that can be leveraged in conjunction with other attacks to disrupt service availability.
Mitigation strategies focus primarily on applying the vendor-provided patch immediately by upgrading the Really Simple Security plugin to version 9.8.3 or later, where input validation for address values has been implemented. For environments where immediate updating is not feasible, administrators should consider implementing web application firewall rules that restrict access to the specific endpoints used by the plugin's AJAX handlers or REST API interfaces responsible for processing these address inputs. Additionally, monitoring database growth rates and setting up alerts for unusual spikes in option table sizes can help detect ongoing exploitation attempts early. Regular auditing of third-party plugins is also recommended to ensure compliance with secure coding standards that mandate strict input validation before any data is persisted to storage systems.