External commands used for retrieving Elytron credentials may fail due to closed error stream.

The CommandCredentialSource closes STD_ERR stream without consuming it.

Elytron unit test CommandCredentialSourceTest (which executes an external java program) hits this issue in some environments. Log contains;

11:30:29,201 TRACE (main) [org.wildfly.security] <CommandCredentialSource.java:114> Exit code from password command = 141

The issue was investigated in this PR. You can find more details there:
https://github.com/wildfly-security/wildfly-elytron/pull/981