CVE-2026-75800 in SAML SSO Plugin
Summary
by MITRE • 09/12/2026
The Frontegg SAML SSO WordPress plugin through 1.0.1 does not verify the signature or issuer of SAML authentication responses before establishing a session, allowing unauthenticated attackers to log in as any user, including administrators, as well as to create arbitrary accounts.
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Analysis
by VulDB Data Team • 09/12/2026
The vulnerability identified in Frontegg SAML SSO WordPress plugin versions up to 1.0.1 represents a critical failure in the implementation of Security Assertion Markup Language authentication protocols. Specifically, the flaw lies within the logic that processes incoming SAML assertions from an identity provider. In a secure SAML configuration, the service provider must rigorously validate two primary components of the assertion: the cryptographic signature and the issuer identifier. The signature verification ensures that the data has not been tampered with during transit and originates from a trusted source. Simultaneously, issuer validation confirms that the authentication request actually came from an authorized identity provider configured in the system settings. In this vulnerable implementation, both checks are omitted or bypassed entirely when processing SAML responses. This omission fundamentally breaks the trust model of federated identity management, rendering the authentication mechanism ineffective against malicious actors who can forge valid-looking assertions without possessing any private keys associated with legitimate providers.
From a technical perspective, this flaw constitutes an insecure direct object reference combined with broken access control mechanisms inherent in improper validation of SAML inputs. The absence of signature verification allows attackers to craft arbitrary XML structures that mimic the format of a genuine SAML assertion. By manipulating specific fields within these forged assertions, such as the NameID or email address attributes, an attacker can dictate which user account should be authenticated upon login. Furthermore, because the plugin does not strictly enforce existing user mappings before session creation, it permits the automatic provisioning of new accounts if the specified identifier does not already exist in the WordPress database. This behavior transforms a simple authentication bypass into a more severe vulnerability where remote unauthenticated attackers can achieve arbitrary code execution equivalent by gaining full administrative privileges or creating backdoor accounts with elevated permissions.
The operational impact of this vulnerability is severe, particularly for organizations relying on single sign-on solutions to secure their WordPress infrastructure. An attacker exploiting this flaw does not require any prior credentials or network proximity beyond internet accessibility to the target site. Once exploited, the attacker can assume the identity of an administrator, thereby gaining complete control over the website's content, plugins, themes, and database. This level of access allows for defacement, data exfiltration, installation of web shells, or pivoting into internal networks if the WordPress instance is integrated with other backend systems. Additionally, the ability to create arbitrary accounts means that persistence mechanisms can be established even after the initial vulnerability patching or credential rotation attempts by administrators. The lack of issuer validation further exacerbates this risk by allowing attackers to spoof any identity provider, making detection through standard logging difficult since the forged assertions appear structurally valid despite lacking proper cryptographic proof of origin.
This issue aligns with Common Weakness Enumeration (CWE) identifiers such as CWE-287 Improper Authentication and CWE-345 Insufficient Verification of Data Authenticity. In terms of attack vectors, it maps to MITRE ATT&CK techniques including T1078 Valid Accounts for initial access via credential stuffing or account creation, and potentially T1190 Exploit Public-Facing Application if the vulnerability is leveraged in conjunction with other web application attacks. The core failure is a deviation from security best practices outlined in SAML 2.0 specifications which mandate strict signature validation to prevent assertion manipulation.
Mitigation strategies must prioritize immediate remediation through software updates or configuration changes where possible. Administrators should upgrade the Frontegg SAML SSO WordPress plugin to version 1.0.2 or later, where these validation checks have been implemented correctly. If upgrading is not immediately feasible, temporary mitigations include disabling the SAML authentication feature entirely and reverting to native WordPress login mechanisms until a patch can be applied. Additionally, implementing Web Application Firewalls with rules capable of detecting malformed XML structures or unusual patterns in POST requests related to SAML endpoints may provide some layer of defense against exploitation attempts. Regular security audits focusing on identity provider configurations and strict adherence to cryptographic validation standards are essential to prevent similar vulnerabilities in federated authentication systems across the organization's digital assets.