Description

Unauthenticated Broken Authentication in Really Simple SSL <= 9.8.0 versions.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.4",
  "pubDate": "2026-09-03T17:17:28.623Z",
  "pubdate": "2026-09-03T17:17:28.623Z",
  "executiveSummary": "A critical unauthenticated broken authentication vulnerability has been identified in the Really Simple SSL plugin, affecting all versions up to and including 9.8.0. This vulnerability permits an attacker to bypass standard authentication protocols without providing valid credentials.\nThe flaw stems from a critical logic error in the authentication verification mechanism, which allows an unauthenticated actor to impersonate any user on the system, including administrative accounts.\nThe impact of this vulnerability is severe, as it facilitates full site takeover, unauthorized access to sensitive data, and complete control over the WordPress environment. The vulnerability is remotely exploitable, requiring no prior authentication, credentials, or interaction with the site administrator.\nDue to the nature of the vulnerability—which targets the core authentication flow of the plugin—the risk implications are categorized as critical. It presents an immediate threat to the confidentiality, integrity, and availability of affected installations. Attackers can leverage this exploit to gain persistent administrative access, execute arbitrary code via administrative plugins, or exfiltrate databases. Organizations utilizing Really Simple SSL are advised to treat this as a high-priority security incident and apply updates or mitigations immediately to prevent potential compromise.",
  "technicalDetails": "The vulnerability resides within the Really Simple SSL authentication logic, specifically in the way the plugin handles user identity verification and login bypass mechanisms. By failing to strictly validate the authenticity of requests intended to simulate or trigger an authentication state, the plugin allows an unauthenticated external entity to inject or manipulate the session initialization process.\nThe root cause is a flaw in the identity verification routines where the code incorrectly trusts user-controllable input or environment variables intended for internal state management. During the login flow, the plugin fails to enforce a cryptographically secure verification check, allowing the system to erroneously treat a malformed or crafted HTTP request as a successful authentication event for a target user ID.\nThe attack flow proceeds as follows: 1. The attacker identifies an installation of Really Simple SSL running version 9.8.0 or earlier. 2. The attacker crafts a request, often involving the manipulation of specific parameters or request headers designed to trigger the vulnerable authentication bypass function. 3. Because the vulnerable function does not properly verify the legitimacy of the authentication attempt, it improperly grants the attacker a session authenticated as the target user. 4. Once the session is established, the attacker gains the privileges associated with that user account. If the target is an administrator, the attacker achieves full administrative control over the WordPress site.\nThe vulnerability is remotely exploitable over the network via standard HTTP/HTTPS protocols, requiring no privileged access to initiate the exploit. Because the authentication mechanism itself is bypassed, there is no requirement for valid credentials or existing session cookies. This bypass occurs at the application layer, effectively circumventing the security perimeter of the WordPress authentication system. Post-exploitation, the attacker can leverage the obtained privileges to perform any action the compromised user is authorized to execute, including modifying site content, installing malicious plugins, modifying system configurations, or accessing sensitive database records. The persistence of the access depends on the attacker's ability to maintain a valid session or create an administrative backdoor, which is readily possible once the initial bypass is achieved."
}