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CVE-2019-18276

Published: 28 November 2019

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.

Priority

Low

CVSS 3 base score: 7.8

Status

Package Release Status
bash
Launchpad, Ubuntu, Debian
Upstream
Released (5.1)
Ubuntu 21.10 (Impish Indri) Not vulnerable
(5.1-1ubuntu1)
Ubuntu 21.04 (Hirsute Hippo) Not vulnerable
(5.1-1ubuntu1)
Ubuntu 20.04 LTS (Focal Fossa) Needed

Ubuntu 18.04 LTS (Bionic Beaver) Needed

Ubuntu 16.04 ESM (Xenial Xerus) Needed

Ubuntu 14.04 ESM (Trusty Tahr) Needed

Patches:
Upstream: https://git.savannah.gnu.org/cgit/bash.git/commit/?h=devel&id=951bdaad7a18cc0dc1036bba86b18b90874d39ff

Notes

AuthorNote
sbeattie
This issue appears to only affect bash when bash is
setuid. Ubuntu does not ship with bash setuid, so this has minimal
impact for Ubuntu users. This is why we have rated the priority
for this issue 'low'.
reproducer steps in the suse bugzilla

References

Bugs