CVE-2026-84775: Really Simple SSL DOS Vulnerability

CVE-2026-84775 Overview

CVE-2026-84775 is an unauthenticated denial of service (DoS) vulnerability affecting the Really Simple SSL WordPress plugin in versions up to and including 9.8.0. The flaw stems from uncontrolled resource consumption [CWE-770], allowing a remote attacker to exhaust server resources without authentication. Exploitation requires no user interaction and can be launched over the network. Successful attacks degrade site availability for legitimate visitors and administrators.

Critical Impact
Remote unauthenticated attackers can trigger resource exhaustion against WordPress sites running vulnerable Really Simple SSL versions, disrupting availability.

Affected Products

Really Simple SSL WordPress plugin versions <= 9.8.0
WordPress sites with the plugin installed and activated
Hosting environments running vulnerable Really Simple SSL deployments

Discovery Timeline

2026-09-02 - CVE-2026-84775 published to NVD
2026-09-02 - Last updated in NVD database

Technical Details for CVE-2026-84775

Vulnerability Analysis

The vulnerability is classified under Uncontrolled Resource Consumption [CWE-770]. Really Simple SSL exposes functionality reachable by unauthenticated network requests that fails to enforce limits on resource allocation. An attacker sending crafted or repeated requests can force the plugin to consume disproportionate CPU, memory, or database resources. The attack results in reduced availability rather than data compromise, aligning with the impact profile of a partial availability loss.

Root Cause

The root cause is missing enforcement of quotas, rate limits, or size checks on inputs processed by the plugin. When the plugin handles attacker-influenced operations without bounding their cost, the underlying PHP worker and database resources become saturated. Refer to the Patchstack Security Vulnerability Assessment for advisory details.

Attack Vector

Exploitation occurs over the network against the WordPress site hosting the plugin. No authentication, privileges, or user interaction are required. Attackers issue HTTP requests to the vulnerable endpoint exposed by Really Simple SSL, causing the server to allocate resources beyond intended thresholds. Sustained or high-volume requests amplify the impact, potentially rendering the site unresponsive.

No verified public proof-of-concept exploit code is available at the time of publication.

Detection Methods for CVE-2026-84775

Indicators of Compromise

Sudden spikes in PHP worker or FastCGI process utilization tied to requests targeting Really Simple SSL endpoints
Elevated database connection counts or slow query logs referencing plugin-related tables
HTTP 5xx errors and request timeouts correlated with unauthenticated traffic from single or distributed sources

Detection Strategies

Inventory WordPress installations to identify Really Simple SSL versions <= 9.8.0
Deploy web application firewall (WAF) rules to flag anomalous request patterns to plugin routes
Baseline normal request volume and alert on deviations targeting plugin-specific URIs

Monitoring Recommendations

Monitor web server access logs for repeated unauthenticated requests to Really Simple SSL endpoints
Track CPU, memory, and database load metrics on WordPress hosts for sustained anomalies
Correlate WAF telemetry with origin logs to identify low-and-slow resource-exhaustion attempts

How to Mitigate CVE-2026-84775

Immediate Actions Required

Update Really Simple SSL to a version above 9.8.0 once the vendor patch is applied
Restrict access to non-essential plugin endpoints using WAF or reverse proxy rules
Enable rate limiting on unauthenticated requests to the WordPress site

Patch Information

Refer to the Patchstack advisory for the fixed version and remediation guidance. Administrators should apply the vendor-supplied update through the WordPress plugin management interface as soon as it is available.

Workarounds

Deploy WAF signatures that rate-limit or block abusive traffic to plugin endpoints
Temporarily deactivate the Really Simple SSL plugin if patching is not immediately possible
Place the WordPress site behind a CDN with request throttling and bot mitigation enabled

bash

# Configuration example: nginx rate limiting for WordPress plugin endpoints
limit_req_zone $binary_remote_addr zone=rssl_limit:10m rate=10r/m;

server {
    location ~* /wp-content/plugins/really-simple-ssl/ {
        limit_req zone=rssl_limit burst=5 nodelay;
        limit_req_status 429;
    }
}