CVE-2025-62610 is an improper authorization vulnerability classified under CWE-285 affecting the Hono JavaScript web framework versions from 1.1.0 up to before 4.10.2. Hono’s JWT Auth Middleware does not natively verify the 'aud' (audience) claim in JSON Web Tokens, which is a critical security check mandated by RFC 7519. The 'aud' claim ensures that a token is accepted only by the intended recipient service. Without this verification, tokens issued for one service can be mistakenly accepted by another service sharing the same issuer and cryptographic keys, leading to confused-deputy or token mix-up attacks. This flaw can allow an attacker to gain unauthorized access to APIs or services by presenting a valid token meant for a different service, thereby compromising confidentiality and integrity of data and operations. The vulnerability does not affect availability and requires user interaction, such as submitting a crafted token. The CVSS v3.1 score is 8.1 (high severity), reflecting network attack vector, low attack complexity, no privileges required, and user interaction needed. The vulnerability was publicly disclosed on October 22, 2025, and patched in Hono version 4.10.2. No known exploits in the wild have been reported yet. Organizations using Hono in multi-service environments must be aware that relying solely on issuer and key validation without audience claim checks is insufficient for secure token validation.

For European organizations, this vulnerability poses a significant risk in environments where multiple services share the same JWT issuer and signing keys but serve different audiences. Attackers can exploit this flaw to gain unauthorized access to services by presenting tokens issued for other services, potentially leading to data breaches, unauthorized actions, and lateral movement within enterprise systems. This can compromise sensitive customer data, intellectual property, and internal APIs, impacting confidentiality and integrity. The risk is particularly acute for organizations adopting microservices architectures or API ecosystems using Hono for authentication. Regulatory compliance frameworks such as GDPR may impose penalties if unauthorized data access occurs. The lack of availability impact reduces the risk of service disruption but does not mitigate the serious confidentiality and integrity concerns. The absence of known exploits suggests a window for proactive mitigation before widespread attacks occur.

1. Upgrade all Hono framework instances to version 4.10.2 or later, where the 'aud' claim verification is implemented and enforced by default. 2. If upgrading immediately is not feasible, implement custom middleware to explicitly validate the 'aud' claim in JWTs against the expected audience for each service, rejecting tokens that do not match. 3. Review and segregate JWT issuers and signing keys per service to minimize token reuse risks across services. 4. Conduct a thorough audit of all services using Hono to identify those sharing issuer and keys and assess exposure. 5. Enhance logging and monitoring to detect anomalous token usage patterns indicative of token mix-up exploitation. 6. Educate development teams on proper JWT validation practices aligned with RFC 7519, emphasizing the importance of audience claim checks. 7. Integrate automated security testing in CI/CD pipelines to verify JWT validation logic correctness. 8. Coordinate with identity providers to ensure tokens issued include correct and consistent 'aud' claims. 9. Prepare incident response plans for potential unauthorized access scenarios stemming from this vulnerability.