You can modify TLS algorithms in CSS 7.6.2 and later versions.
Add the opendistro_security.ssl.http.enabled_ciphers parameter and set it to ['TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256', 'TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384'].
If the parameter value contains multiple algorithm protocols, enclose the value with a pair of square brackets ([]). If the parameter value is a single algorithm protocol, enclose the value with a pair of single quotation marks(' ').
If the Status is Succeeded in the parameter modification list, the modification has been saved.