The mkdir procedure of GNU Guile, an implementation of the Scheme programming language, temporarily changed the process' umask to zero. During that time window, in a multithreaded application, other threads could end up creating files with insecure permissions. For example, mkdir without the optional mode argument would create directories as 0777.
It was reported that the REPL server is vulnerable to the HTTP inter- protocol attack. This constitutes a remote code execution vulnerability for developers running a REPL server that listens on a loopback device or private network. Applications that do not run a REPL server, as is usually the case, are unaffected.