CVE-2025-46647 is an authentication bypass vulnerability identified in the openid-connect plugin of Apache APISIX, an open-source API gateway and microservices management platform maintained by the Apache Software Foundation. The vulnerability arises specifically when the openid-connect plugin is configured to use introspection mode for token validation. The issue manifests under a particular set of conditions: the authentication service connected to the openid-connect plugin must support multiple issuers, and these issuers must share the same private key while relying solely on the issuer identifier to differentiate authentication contexts. Under these conditions, an attacker who has a valid account on one issuer can exploit the vulnerability to gain unauthorized access to another issuer's resources, effectively bypassing authentication controls. This occurs because the system assumes certain data (such as the private key) to be immutable and unique per issuer, but the shared private key undermines this assumption, allowing token introspection to be fooled. The vulnerability affects all versions of Apache APISIX prior to 3.12.0, with the vendor recommending an upgrade to version 3.12.0 or later to remediate the issue. No public exploits have been reported in the wild as of the publication date. The vulnerability is classified under CWE-302, which relates to improper authentication mechanisms that allow bypassing intended access controls.

For European organizations utilizing Apache APISIX as their API gateway, particularly those leveraging the openid-connect plugin in introspection mode with multi-issuer authentication services sharing private keys, this vulnerability poses a significant risk. Successful exploitation would allow attackers with legitimate credentials on one issuer to impersonate users on another issuer, potentially gaining unauthorized access to sensitive applications, data, or services. This could lead to data breaches, unauthorized transactions, or lateral movement within enterprise networks. Given the critical role of API gateways in managing microservices and enforcing security policies, this bypass could undermine the integrity and confidentiality of internal and external communications. The impact is heightened in sectors with stringent regulatory requirements such as finance, healthcare, and government, where identity and access management are crucial. Additionally, organizations using shared authentication infrastructures or federated identity providers that do not segregate private keys per issuer are particularly vulnerable. The absence of known exploits in the wild reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits following public disclosure.

To mitigate this vulnerability, European organizations should promptly upgrade Apache APISIX to version 3.12.0 or later, where the issue has been addressed. Beyond upgrading, organizations should review their openid-connect plugin configurations to ensure that each issuer uses a unique private key rather than sharing keys across multiple issuers. This architectural change prevents the assumption of immutable data from being violated. Additionally, organizations should audit their authentication services to verify proper issuer segregation and token validation logic. Implementing strict key management policies and rotating keys regularly can further reduce risk. Monitoring authentication logs for unusual cross-issuer login attempts can help detect exploitation attempts. Where possible, organizations should consider deploying additional layers of authentication, such as multi-factor authentication (MFA), to reduce the impact of credential compromise. Finally, conducting penetration testing focused on authentication bypass scenarios can validate the effectiveness of mitigations.