EUVD-2026-54199
GHSA-hxv9-fx39-qg4c
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Network-reachable bypass needing no privileges or interaction; integrity impact is low as only login form access is gained, not data or system state.
Primary rating from Vendor (wpscan).
CVSS VectorVendor: wpscan
Lifecycle Timeline
3DescriptionCVE.org
The Security Optimizer WordPress plugin from 1.5.8 to 1.6.4 does not correctly validate requests to its optional IP-based login restriction feature, allowing the restriction to be bypassed so that unauthenticated requests from non-allowlisted IP addresses can reach and use the login form, defeating the access control the administrator configured.
AnalysisAI
Security Optimizer WordPress plugin versions 1.5.8 through 1.6.4 expose a bypass in its optional IP-based login restriction feature, allowing unauthenticated remote users from non-allowlisted IP addresses to reach the WordPress login form despite administrator-configured access controls. The CVSS vector (AV:N/AC:L/PR:N/UI:N) confirms trivial network exploitability with no authentication or user interaction required to perform the bypass. No public exploit has been identified at time of analysis and this vulnerability is not listed in CISA KEV; however, sites relying on the IP restriction as a primary login protection layer face elevated credential attack exposure.
Technical ContextAI
The Security Optimizer plugin is a WordPress hardening plugin that offers an optional feature to restrict access to the wp-login.php login endpoint by IP allowlist, preventing non-allowlisted addresses from reaching the authentication interface. The vulnerability is a request validation flaw in how the plugin evaluates whether an incoming request originates from a permitted IP - likely a logic error in IP header parsing (e.g., trusting spoofable headers such as X-Forwarded-For or X-Real-IP) or an incomplete matching condition. Although CWE is listed as N/A in the advisory, this class of flaw is conceptually consistent with CWE-290 (Authentication Bypass by Spoofing) or CWE-807 (Reliance on Untrusted Inputs in a Security Decision). The affected product range per EUVD-2026-54199 is Security Optimizer 1.5.8 up to but not including 1.6.5.
RemediationAI
Update the Security Optimizer WordPress plugin to version 1.6.5 or later, which contains the vendor-released patch resolving the IP allowlist validation flaw. Details are available at https://wpscan.com/vulnerability/ab14b11c-96ab-4d07-89e0-1d67e4314267/. As an interim workaround prior to patching, enforce the same IP restriction at the web server or network perimeter layer - for example, using nginx location directives or Apache mod_authz_host rules on wp-login.php, or firewall ACLs blocking login endpoint access from non-allowlisted IPs - which operates independently of the plugin and is not subject to this bypass. Note that web server-level controls require infrastructure access and may affect legitimate users if allowlists are misconfigured. Enabling two-factor authentication on the WordPress site provides independent protection against credential attacks even if the IP restriction is bypassed, with the trade-off of added user friction.
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Same weakness CWE-693 – Protection Mechanism Failure
View allSame technique Authentication Bypass
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External POC / Exploit Code
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