Secure Socket Layer (SSL)

Applies to. The term matters to any entity that sends PAN over open, public networks, which Requirement 4 governs, and to any entity relying on an encrypted channel as a security control elsewhere in the Cardholder Data Environment. Outside Appendix A2, PCI DSS v4.0.1 does not name SSL in its requirement text; it asks for strong cryptography and secure protocols, and SSL fails that test on every version. Appendix A2 deals with SSL and early TLS directly, and only for existing card-present point-of-sale point-of-interaction terminals, and the termination points they connect to, that are verified as not susceptible to any known exploits for those protocols. New terminal implementations may not use them as a security control.

Example. A merchant moves its online shop to a host that supports current TLS, but the back-end integration to its payment gateway still uses an old library configured to accept SSL 3.0 for compatibility. The quarterly external scan reports the server as accepting SSL, and the merchant does not get a passing scan until the setting is removed and the library replaced.

Limits. SSL is not a version of TLS, though the two are often lumped together, and an 'SSL certificate' does not mean the connection uses SSL: it is an X.509 certificate that works with either protocol. Disabling SSL alone is not enough. TLS 1.0 and 1.1 are grouped with it as early TLS under the Council's migration guidance and are treated the same way. A server that offers current TLS but still allows a fallback to SSL or early TLS has not fixed the problem, because a downgrade attack can force the weaker protocol.