CVE-2018-20839

NameCVE-2018-20839
Descriptionsystemd 242 changes the VT1 mode upon a logout, which allows attackers to read cleartext passwords in certain circumstances, such as watching a shutdown, or using Ctrl-Alt-F1 and Ctrl-Alt-F2. This occurs because the KDGKBMODE (aka current keyboard mode) check is mishandled.
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, bugtraq, EDB, Metasploit, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, Mageia, GitHub code/issues, web search, more)
NVD severitymedium

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
plymouth (PTS)stretch0.9.2-4vulnerable
buster0.9.4-1.1fixed
bullseye, sid0.9.4-3fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
plymouthsource(unstable)0.9.4-1low

Notes

[stretch] - plymouth <no-dsa> (Minor issue)
[jessie] - plymouth <no-dsa> (Minor issue)
https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1803993
https://github.com/systemd/systemd/commit/9725f1a10f80f5e0ae7d9b60547458622aeb322f
https://github.com/systemd/systemd/pull/12378
The fix for https://bugs.debian.org/929116 introduced a regression, cf.
https://bugs.debian.org/929229 .
Issue was originally fixed for unstable in 241-4 but was reverted in 241-5
https://gitlab.freedesktop.org/xorg/xserver/issues/857
Upstream from systemd claimed originally it's not an issue in systemd, but
might revisit. Furthermore the issue might be fixed in the xorg xserver.
Tentative merge request: https://gitlab.freedesktop.org/xorg/xserver/merge_requests/241
Further analysis on the problem: https://gitlab.freedesktop.org/xorg/xserver/issues/857#note_201402
plymouth fix: https://gitlab.freedesktop.org/plymouth/plymouth/commit/28ee4012c94b4045b97e5a2a66f66b7688b2dff3 (0.9.4)
The plymouth fix does not seem to be enough though, cf.
https://gitlab.freedesktop.org/xorg/xserver/issues/857#note_220255

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