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.

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