When using an OCSP responder Apache Tomcat Native 1.2.0 to 1.2.16 and 1.1.23 to 1.1.34 did not correctly handle invalid responses. This allowed for revoked client certificates to be incorrectly identified. It was therefore possible for users to authenticate with revoked certificates when using mutual TLS. Users not using OCSP checks are not affected by this vulnerability.
A vulnerability in the Online Certificate Status Protocol (OCSP) responder of Apache Tomcat Native could allow an authenticated, remote attacker to gain unauthorized access to a targeted system.
The vulnerability exists because the affected software improperly handles invalid responses. As a result, revoked certificates may not be properly identified. An attacker could exploit this vulnerability by using a revoked certificate to authenticate to the affected application when using a mutual Transport Layer Security (TLS) connection. A successful exploit could allow the attacker to gain unauthorized access to the system, which could be used to conduct further attacks.
Apache confirmed the vulnerability and released software updates.
Administrators are advised to apply the appropriate updates.
Administrators are advised to allow only trusted users to have network access.
Administrators are advised to run both firewall and antivirus applications to minimize the potential of inbound and outbound threats.
Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.
Administrators can help protect affected systems from external attacks by using a solid firewall strategy.
Administrators are advised to monitor affected systems.
To exploit this vulnerability, the attacker must have user-level access to the targeted system. This access requirement may reduce the likelihood of a successful exploit.
Systems that are not using OCSP checks are not affected by this vulnerability.