CVE-2025-12466 identifies an authentication bypass vulnerability categorized under CWE-288 in the Drupal Simple OAuth (OAuth2) & OpenID Connect module. This module, used for OAuth2 and OpenID Connect authentication flows in Drupal, versions 6.0.0 up to but not including 6.0.7, contains a flaw that allows attackers to circumvent authentication mechanisms by leveraging an alternate path or communication channel. The vulnerability does not require any privileges or user interaction, making it remotely exploitable over the network (AV:N, PR:N, UI:N). The CVSS v3.1 base score is 7.5, reflecting high severity primarily due to the impact on confidentiality (C:H), while integrity and availability remain unaffected (I:N, A:N). The issue arises because the module fails to properly validate authentication requests when routed through alternate channels, allowing unauthorized actors to gain access without valid credentials. Although no exploits have been reported in the wild yet, the vulnerability poses a significant risk to systems relying on this module for secure authentication. The lack of a patch link suggests that a fix is either pending or recently released in version 6.0.7. Organizations using affected versions should prioritize upgrading and review their authentication logs for suspicious activity. This vulnerability could be leveraged to access sensitive user data or internal resources protected by OAuth2/OpenID Connect authentication flows within Drupal environments.

For European organizations, the primary impact of CVE-2025-12466 is unauthorized access to systems and data protected by the Drupal Simple OAuth module. This can lead to exposure of sensitive personal data, intellectual property, or internal communications, violating GDPR and other data protection regulations. Since the vulnerability allows bypassing authentication without user interaction or privileges, attackers can stealthily access restricted areas, potentially leading to data breaches or further lateral movement within networks. Organizations in sectors such as government, finance, healthcare, and critical infrastructure that rely on Drupal for web services and use OAuth2/OpenID Connect for authentication are particularly vulnerable. The confidentiality breach could result in regulatory fines, reputational damage, and operational disruptions. Additionally, the ease of exploitation increases the likelihood of automated scanning and attacks targeting vulnerable Drupal instances across Europe.

1. Immediately upgrade the Drupal Simple OAuth (OAuth2) & OpenID Connect module to version 6.0.7 or later once the patch is available to remediate the vulnerability. 2. Until the patch is applied, restrict access to the affected authentication endpoints using network-level controls such as IP whitelisting or VPN-only access. 3. Implement enhanced logging and monitoring on authentication services to detect unusual or anomalous authentication attempts, especially those that might indicate exploitation of alternate paths. 4. Conduct a thorough audit of existing OAuth2/OpenID Connect configurations to ensure no insecure fallback or alternate authentication channels are enabled. 5. Employ Web Application Firewalls (WAFs) with custom rules to detect and block suspicious requests targeting the vulnerable module. 6. Educate development and security teams about the vulnerability to ensure rapid response and patch management. 7. Review and tighten access control policies around Drupal administrative interfaces and sensitive data repositories to limit potential damage from unauthorized access.