Ubuntu Security Notice 5380-1 - It was discovered that Bash did not properly drop privileges when the binary had the setuid bit enabled. An attacker could possibly use this issue to escalate privileges.
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Gentoo Linux Security Advisory 202105-34 - A vulnerability in Bash may allow users to escalate privileges. Versions less than 5.0_p11-r1 are affected.
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Red Hat Security Advisory 2021-1679-01 - The bash packages provide Bash, which is the default shell for Red Hat Enterprise Linux.
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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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