CVE-2018-8020 in Tomcat Native
Summary
by MITRE
Apache Tomcat Native 1.2.0 to 1.2.16 and 1.1.23 to 1.1.34 has a flaw that does not properly check OCSP pre-produced responses, which are lists (multiple entries) of certificate statuses. Subsequently, revoked client certificates may not be properly identified, allowing for users to authenticate with revoked certificates to connections that require mutual TLS. Users not using OCSP checks are not affected by this vulnerability.
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Analysis
by VulDB Data Team • 04/28/2023
Apache Tomcat Native versions 1.2.0 through 1.2.16 and 1.1.23 through 1.1.34 contain a critical flaw in their OCSP (Online Certificate Status Protocol) implementation that undermines the security of mutual TLS authentication. This vulnerability resides in the certificate status validation mechanism where the system fails to properly validate pre-produced OCSP responses containing multiple entries. The flaw specifically affects how the software processes OCSP response lists, allowing revoked certificates to bypass proper status checking and remain accepted for authentication purposes. This represents a significant deviation from the expected behavior defined in RFC 6960 for OCSP response processing, where each response must be validated against the certificate authority's trust store and properly parsed for multiple certificate status entries. The vulnerability is categorized under CWE-295 which addresses improper certificate validation and falls within the ATT&CK technique T1552.001 for credentials from password storage devices, as compromised certificates could be used to gain unauthorized access to systems protected by mutual TLS.
The operational impact of this vulnerability extends beyond simple authentication bypass to create a potential attack vector for credential compromise and man-in-the-middle scenarios. When mutual TLS is configured with OCSP checking enabled, attackers can exploit this flaw to present revoked client certificates that will be accepted by the system, effectively allowing unauthorized authentication. This creates a dangerous situation where the entire certificate-based authentication system becomes ineffective, as the security controls designed to prevent use of compromised certificates are bypassed. The vulnerability particularly affects environments where client certificate authentication is used for sensitive systems such as API gateways, internal service communications, and privileged access points where mutual TLS is enforced. Organizations using Tomcat Native with OCSP validation enabled are at risk of having their security boundaries compromised, as revoked certificates that should be rejected are accepted due to the improper response list validation.
Mitigation strategies for this vulnerability require immediate attention and systematic implementation across affected systems. Organizations should upgrade to Tomcat Native versions 1.2.17 or 1.1.35, which contain the patched OCSP response validation logic that properly handles multiple certificate entries in pre-produced responses. Additionally, system administrators should consider implementing alternative certificate validation methods such as CRL (Certificate Revocation List) checking where OCSP validation is not critical, or configure the system to disable OCSP checks entirely if mutual TLS authentication is not strictly required. The remediation process should include comprehensive testing of certificate validation workflows to ensure that revoked certificates are properly rejected and that the updated system correctly processes OCSP responses with multiple entries. Security teams should also monitor for any potential exploitation attempts by reviewing authentication logs for unusual patterns or certificate usage that might indicate an attempt to leverage this vulnerability. Regular security assessments should be conducted to verify that all certificate-based authentication systems are properly configured and that the patched versions are correctly deployed across all affected environments, ensuring that the integrity of mutual TLS connections is maintained against certificate compromise attacks.