CVE-2026-77998 in SAML SSO Extension
Summary
by MITRE • 08/25/2026
Joomla Extension - miniorange.com - Unauthenticated Authentication Bypass via SAMLResponse Parameter in miniOrange SAML SSO < 11.0.2, SAML SP Single Sign On – Login with ADFS < 6.4, SAML SP Single Sign On – SAML SSO login with Google Apps < 6.4 - This is due to the mo_saml_validate_signature() function performing a loose boolean check on the raw tri-state integer returned by PHP's openssl_verify(), causing an error return value of -1 to be evaluated as truthy and therefore treated as a successful signature verification. This makes it possible for unauthenticated attackers to log in as any existing Joomla user, including administrators, by submitting a crafted SAMLResponse containing an attacker-controlled NameID and a deliberately malformed signature value that triggers an OpenSSL processing error — bypassing verification entirely and resulting in wp_set_auth_cookie() being called for the targeted account.
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Analysis
by VulDB Data Team • 08/25/2026
The vulnerability identified in various miniOrange Joomla extensions, including versions prior to 11.0.2 for SAML SSO, version 6.4 or earlier for Login with ADFS, and version 6.4 or earlier for Google Apps integration, represents a critical authentication bypass flaw rooted in improper error handling within the PHP cryptographic verification process. This issue specifically affects systems relying on Security Assertion Markup Language (SAML) protocols to facilitate Single Sign-On operations, allowing unauthenticated attackers to assume the identity of any existing user account without providing valid credentials or possessing legitimate security tokens. The core technical defect lies in the implementation of the mo_saml_validate_signature function, which serves as the gatekeeper for verifying the integrity and authenticity of incoming SAML assertions. When a SAMLResponse is submitted by an external Identity Provider or attacker-controlled endpoint, this function invokes PHP's openssl_verify() method to cryptographically validate the digital signature attached to the assertion data.
PHP's openssl_verify() function returns distinct integer values to indicate the outcome of the verification process: it typically returns 1 for a successful match, 0 if the signature is invalid, and -1 in the event that an error occurs during processing, such as when the provided public key is unsupported or malformed. The vulnerability arises because the extension developers implemented a loose boolean check on this return value rather than explicitly checking against the expected success state of one. In PHP's type juggling logic, any non-zero integer evaluates to true in a conditional statement. Consequently, while a valid signature returning 1 correctly passes verification, an error condition returning -1 is also evaluated as truthy and erroneously treated as a successful authentication event. This logical flaw effectively neutralizes the cryptographic protection mechanism, allowing attackers to bypass signature validation entirely by triggering processing errors through carefully crafted input data.
The operational impact of this vulnerability is severe, enabling unauthenticated remote code execution in terms of identity theft and privilege escalation. An attacker can construct a malicious SAMLResponse payload that includes an attacker-controlled NameID field specifying the target username, such as admin or any other existing user account within the Joomla installation. By deliberately introducing malformed signature data into this response, the attacker forces the openssl_verify() function to return -1 due to processing errors. Due to the aforementioned boolean logic flaw, the application accepts this error state as a valid authentication success and proceeds to establish a session for the targeted user. This process culminates in the invocation of wp_set_auth_cookie(), which is likely a misstatement in the original description referring to Joomla's equivalent session creation function, thereby granting the attacker full access to the compromised account with all associated permissions and privileges.
From a classification perspective, this vulnerability aligns closely with CWE-287 Improper Authentication, as it involves failing to properly verify credentials or security tokens before establishing an authenticated session. It also relates to CWE-94 Improper Control of Generation of Code (Code Injection) in the broader sense that logic flaws allow unauthorized execution of administrative functions, though more specifically it fits CWE-613 Insufficient Session Expiration and CWE-807 Reliance on Untrusted Inputs in Security Decision Making. In terms of the MITRE ATT&CK framework, this exploit maps to T1078 Valid Accounts, where adversaries use legitimate credentials or identities to access resources without detection, and specifically leverages a flaw in authentication mechanisms similar to techniques described under T1621 Multi-Factor Authentication Request Interception if viewed through the lens of bypassing multi-factor controls inherent in SAML flows. The attack vector is classified as Remote (Network) with Low Complexity, requiring no prior access or user interaction beyond submitting HTTP requests containing the crafted XML payloads.
Mitigation strategies must prioritize immediate patching and defensive coding practices to address both the specific code defect and broader architectural weaknesses. Administrators should upgrade all affected miniOrange Joomla extensions to versions 11.0.2 or later for SAML SSO, and version 6.4 or later for ADFS and Google Apps integrations, as these releases contain fixes that enforce strict equality checks against the expected return value of one from openssl_verify(). For organizations unable to patch immediately due to dependency constraints, implementing a Web Application Firewall (WAF) rule set capable of detecting anomalous SAML responses with malformed signatures or unexpected XML structures can provide a layer of defense. Additionally, developers should adopt defensive programming standards that explicitly validate cryptographic outcomes against expected constants rather than relying on loose boolean evaluations, ensuring that error states are treated as failures and not successes. Regular security audits focusing on authentication logic and third-party library integration points are essential to prevent similar vulnerabilities in future development cycles.