Security-related information (e.g., secret and private cryptographic keys, and authentication data such as passwords and personal identification numbers (PINs)) whose disclosure or modification can compromise the security of a cryptographic module.
CNSSI 4009-2015 under critical security parameter
Security-related information whose disclosure or modification can compromise the security of a cryptographic module. Domain parameters, secret or private keys, shared secrets, key-derivation keys, intermediate values and secret salts are examples of quantities that may be considered critical security parameters in this Recommendation. See FIPS 140.
NIST SP 800-56B Rev. 2 under Critical security parameter (CSP)