CVE-2026-93578 in Apache Camel Spring Boot
Summary
by MITRE • 09/18/2026
Missing Extended Key Usage (EKU) check in OCSP Client allows certificate revocation bypass
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Analysis
by VulDB Data Team • 09/18/2026
The absence of an Extended Key Usage validation within the Online Certificate Status Protocol client implementation represents a critical security deficiency that undermines the fundamental trust model of Public Key Infrastructure systems. In standard TLS operations, certificates are bound to specific purposes through EKU extensions such as serverAuth or clientAuth. When an OCSP responder returns a status indicating that a certificate is valid and not revoked, the relying party must verify that this certificate was actually intended for use in the current context. Without checking whether the certificate possesses the appropriate Extended Key Usage extension corresponding to the role being performed, the system fails to enforce purpose-bound constraints. This oversight allows an attacker who has obtained or forged a certificate with limited privileges to exploit it in contexts where such access is not authorized, effectively bypassing intended security boundaries established by the Certificate Authority and relying party policies.
This vulnerability directly facilitates unauthorized access scenarios that align closely with CWE-295 Improper Certification Path Validation and CWE-807 Reliance on Untrusted Inputs in a Security Context. By neglecting to validate the EKU extension, the software treats all valid certificates as equally suitable for authentication regardless of their designated purpose. For instance, an attacker possessing a certificate explicitly issued for code signing or email protection could potentially use it to authenticate against a service expecting only server-side TLS connections if the OCSP check passes without verifying usage constraints. This behavior contradicts RFC 5280 which mandates that relying parties must verify EKU extensions when present and applicable to the operation being performed. The failure to perform this check creates a logical flaw where cryptographic validity is mistaken for functional authorization, allowing malicious actors to leverage certificates outside their intended scope.
The operational impact of this vulnerability can be severe depending on the deployment environment. In enterprise networks relying heavily on mutual TLS or strict certificate-based access controls, an attacker with a compromised or improperly issued certificate could gain unauthorized entry into protected systems. This bypasses multi-factor authentication mechanisms that rely on client certificates as one factor, potentially leading to data exfiltration, lateral movement within internal networks, or privilege escalation if the misused certificate has broader permissions than anticipated. Furthermore, this flaw erodes trust in PKI-based security architectures because it demonstrates a gap between theoretical policy enforcement and actual implementation behavior. Attackers can exploit this by presenting certificates that are technically valid according to signature chains but semantically invalid for the specific service being accessed, thereby circumventing access control lists tied to certificate attributes rather than just revocation status.
Mitigation requires immediate patching of the OCSP client logic to enforce strict EKU validation prior accepting a positive revocation response as sufficient proof of trust. Developers must ensure that the application explicitly checks whether the presented certificate contains an Extended Key Usage extension and verifies that at least one usage matches the expected role for the current connection, such as verifying serverAuth for TLS servers or clientAuth for mutual authentication scenarios. If no EKU is present in some legacy certificates where it might be omitted by design, fallback policies should still restrict usage based on other contextual indicators rather than assuming universal validity. Additionally organizations should implement defense-in-depth strategies including strict certificate pinning and regular audits of PKI configurations to ensure that all components involved in the validation chain adhere to RFC 5280 standards. This vulnerability also maps to MITRE ATT&CK technique T1649 Steal or Forge Authentication Certificates as it enables attackers to misuse legitimately issued credentials for unintended purposes, highlighting the need for comprehensive certificate lifecycle management and rigorous implementation of cryptographic best practices across all security-sensitive applications.