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DFHSO0123 Return code 412 received from 'gsk_secure_socket_init'

Troubleshooting


Problem

You receive message DFHSO0123 with return code 412 when trying to upgrade your CICS Transaction Server for z/OS (CICS TS) region and would like to know the meaning of return code 412.

Symptom

DFHSO0123 Return code 412 received from function 'gsk_secure_socket_init' of System SSL. Reason: Unsupported operation.
DFHWB0732 CWXN CICS Web attach processing encountered a sockets I/O error while receiving a client request.

Cause

The SSL function return code 412 means GSK_ERR_UNSUPPORTED, the SSL handshake is not successful because of an unsupported protocol or certificate type. In this case, Secure Sockets Layer (SSL) V2 was being used. However, it is not supported.

Resolving The Problem

Use a supported release of  the Transport Layer Security (TLS) protocol with CICS TS.
  • For CICS TS 6.1 and higher, the supported TLS releases are documented in CICS TS 6.x documentation in topic Transport layer Security (TLS) as follows:   

    CICS® TS supports the Transport Layer Security (TLS) protocol. ... Specifically, CICS supports TLS 1.1, 1.2 and 1.3. TLS 1.1 is stabilized. For more information, see Stabilization notices and discontinued functions.

    Support for TLS 1.0 is removed as of CICS TS 6.1. Support for TLS 1.1 is removed as of CICS TS beta (the release after CICS TS 6.2). Consider using TLS 1.2 or TLS 1.3 (RFC 8446) that provide increased security for TCP/IP connections using Customizing encryption negotiations.
  • For CICS TS 5.4, 5.5, and 5.6, the supported releases are documented in the CICS TS 5.4, 5.5, and 5.6 documentation in topic Support for security protocols as follows: 

    CICS® supports the Secure Sockets Layer and Transport Layer Security protocols.

    Specifically, CICS supports TLS 1.0, TLS 1.1, and TLS 1.2. For more details of these protocols, see the relevant RFC:

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Product Synonym

CICS/TS CICS TS CICS Transaction Server

Document Information

Modified date:
05 January 2026

UID

swg21249100

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