CVE-2025-12466 identifies a critical authentication bypass vulnerability in the Drupal Simple OAuth (OAuth2) & OpenID Connect module, specifically affecting versions from 6.0.0 up to but not including 6.0.7. The vulnerability is categorized under CWE-288, which involves bypassing authentication mechanisms by exploiting alternate paths or channels that were not properly secured or validated. In this case, the module responsible for handling OAuth2 and OpenID Connect authentication flows in Drupal fails to adequately restrict access, allowing an attacker to circumvent authentication controls. This could be achieved by manipulating request paths, headers, or parameters to access protected resources without valid credentials. The absence of a CVSS score indicates the vulnerability is newly disclosed, with no public exploits reported yet. However, the impact is significant because authentication bypass can lead to unauthorized access, data exposure, and potential privilege escalation within Drupal-based applications. The affected product is widely used in web applications for secure API access and user authentication, making this a high-risk issue for organizations relying on these authentication standards. The vulnerability was published on October 29, 2025, and no official patches or fixes are linked yet, emphasizing the need for immediate attention once updates are released. The technical details confirm the flaw resides in the authentication logic of the Simple OAuth module, which is critical for maintaining secure access control.

For European organizations, the impact of CVE-2025-12466 can be severe. Drupal is a popular content management system across Europe, used by government agencies, educational institutions, and private enterprises. The Simple OAuth module is commonly employed to integrate OAuth2 and OpenID Connect authentication, which are standards for secure delegated access. An authentication bypass could allow attackers to gain unauthorized access to sensitive data, internal APIs, or administrative functions without valid credentials. This compromises confidentiality and integrity of information and could lead to further exploitation such as data theft, defacement, or lateral movement within networks. The vulnerability could disrupt availability if attackers manipulate authentication flows to lock out legitimate users or cause service interruptions. Given the widespread use of Drupal in critical sectors, the risk extends to national infrastructure, public services, and commercial operations. The lack of known exploits currently reduces immediate threat but does not diminish the urgency for mitigation, as attackers may develop exploits rapidly after disclosure. Organizations failing to patch promptly may face regulatory consequences under GDPR if personal data is compromised.

1. Immediately monitor Drupal Simple OAuth module updates and apply version 6.0.7 or later as soon as it is released to address this vulnerability. 2. Until patches are available, implement strict access controls and network segmentation to limit exposure of Drupal authentication endpoints. 3. Conduct a thorough review of authentication flows and logs to detect any anomalous or unauthorized access attempts, focusing on unusual request paths or headers. 4. Employ Web Application Firewalls (WAFs) with custom rules to block suspicious requests that attempt to exploit alternate authentication paths. 5. Restrict OAuth2 and OpenID Connect token issuance to trusted clients and enforce strong client authentication mechanisms. 6. Educate development and security teams about the risks of alternate path authentication bypass and encourage secure coding practices for authentication modules. 7. Perform penetration testing and vulnerability assessments on Drupal instances to identify any residual or related authentication weaknesses. 8. Maintain an incident response plan ready to contain and remediate any exploitation attempts swiftly.