CVE-2025-58362 is a high-severity vulnerability affecting the Hono JavaScript web application framework versions 4.8.0 through 4.9.5. The flaw resides in the getPath utility function, which is responsible for parsing request URLs. The original implementation used fixed character offsets to extract the path from incoming HTTP requests. This approach is fragile and can be exploited by crafting malformed absolute-form Request-URIs that cause incorrect path extraction. Such path confusion can lead to bypassing proxy-level Access Control Lists (ACLs), such as Nginx location blocks, which are commonly used to restrict access to sensitive endpoints like /admin. By exploiting this flaw, an attacker can potentially gain unauthorized access to protected resources without authentication or user interaction. The vulnerability impacts confidentiality primarily, as unauthorized access to sensitive administrative data could occur, while integrity and availability are not directly affected. The issue is fixed in version 4.9.6 of Hono. The CVSS v3.1 score is 7.5, reflecting a network attack vector, low attack complexity, no privileges or user interaction required, and a high impact on confidentiality. No known exploits are currently reported in the wild, but the vulnerability presents a significant risk to applications relying on Hono for routing and access control.

For European organizations using the Hono framework in the affected versions, this vulnerability poses a significant risk of unauthorized access to sensitive administrative endpoints protected by proxy ACLs. If exploited, attackers could bypass security controls and access confidential data, potentially leading to data breaches, regulatory non-compliance (e.g., GDPR violations), and reputational damage. The impact is especially critical for organizations in sectors with stringent data protection requirements such as finance, healthcare, and government. Since the vulnerability does not require authentication or user interaction, it can be exploited remotely and at scale, increasing the threat surface. The confidentiality breach could expose sensitive internal configurations, user data, or administrative controls, which could be leveraged for further attacks. However, the vulnerability does not directly affect data integrity or system availability, limiting the scope of impact to unauthorized data disclosure.

European organizations should immediately upgrade all Hono framework instances to version 4.9.6 or later, where the vulnerability is patched. Until upgrades are completed, organizations should implement additional proxy-level validation and filtering to detect and block malformed absolute-form Request-URIs that could trigger path confusion. Reviewing and tightening Nginx or other proxy ACL configurations to include more robust pattern matching and fallback rules can help mitigate bypass attempts. Application-level access controls should be enforced as a defense-in-depth measure, ensuring that sensitive endpoints require proper authentication and authorization regardless of proxy ACLs. Logging and monitoring should be enhanced to detect unusual request patterns indicative of exploitation attempts. Security teams should conduct audits of all applications using Hono to identify affected versions and prioritize patching. Finally, organizations should consider deploying Web Application Firewalls (WAFs) with custom rules to detect and block suspicious URL parsing anomalies related to this vulnerability.