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 (attack range: remote)
Debian Bugs929116

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
systemd (PTS)jessie215-17+deb8u7vulnerable
jessie (security)215-17+deb8u13vulnerable
stretch (security), stretch232-25+deb9u11vulnerable
buster, sid241-5vulnerable

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

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
systemdsource(unstable)(unfixed)medium929116

Notes

[stretch] - systemd <no-dsa> (Minor issue)
[jessie] - systemd <no-dsa> (Not reproducible without Ubuntu-style persistant VT1 greeter; too invasive to fix)
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 introduced a regression, cf. https://bugs.debian.org/929229
Issue was originally fixed for unstable in 241-4 but was reverted in 241-5

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