Oracle Linux: CVE-2019-18276: ELSA-2021-1679: bash security and bug fix update (LOW)

An issue was discovered in disable_priv_mode in shell.c in GNU Bash through 5.0 patch 11. By default, if Bash is run with its effective UID not equal to its real UID, it will drop privileges by setting its effective UID to its real UID. However, it does so incorrectly. On Linux and other systems that support "saved UID" functionality, the saved UID is not dropped. An attacker with command execution in the shell can use "enable -f" for runtime loading of a new builtin, which can be a shared object that calls setuid() and therefore regains privileges. However, binaries running with an effective UID of 0 are unaffected.
A privilege escalation vulnerability was found in bash in the way it dropped privileges when started with an effective user id not equal to the real user id. Bash may be vulnerable to this flaw if the setuid permission is set and the owner of the bash program itself is a non-root user. A local attacker could exploit this flaw to escalate their privileges on the system.