CVE-2016-1908

NameCVE-2016-1908
DescriptionThe client in OpenSSH before 7.2 mishandles failed cookie generation for untrusted X11 forwarding and relies on the local X11 server for access-control decisions, which allows remote X11 clients to trigger a fallback and obtain trusted X11 forwarding privileges by leveraging configuration issues on this X11 server, as demonstrated by lack of the SECURITY extension on this X11 server.
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)
ReferencesDLA-1500-1
NVD severityhigh (attack range: remote)

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
openssh (PTS)jessie1:6.7p1-5+deb8u4vulnerable
jessie (security)1:6.7p1-5+deb8u8fixed
stretch1:7.4p1-10+deb9u7fixed
stretch (security)1:7.4p1-10+deb9u6fixed
buster1:7.9p1-10fixed
bullseye, sid1:8.0p1-6fixed

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

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
opensshsource(unstable)1:7.2p1-1high
opensshsourcejessie1:6.7p1-5+deb8u6highDLA-1500-1

Notes

[wheezy] - openssh <no-dsa> (Minor issue)
[squeeze] - openssh <no-dsa> (Minor issue)
Upstream commit: https://anongit.mindrot.org/openssh.git/commit/?id=ed4ce82dbfa8a3a3c8ea6fa0db113c71e234416c
which needs to be applied after: https://anongit.mindrot.org/openssh.git/commit/?id=f98a09cacff7baad8748c9aa217afd155a4d493f
Background information on X11 SECURITY extension and SSH: https://thejh.net/written-stuff/openssh-6.8-xsecurity
https://lists.mindrot.org/pipermail/openssh-unix-dev/2016-January/034684.html
Red Hat Bugzilla entry: https://bugzilla.redhat.com/show_bug.cgi?id=1298741
vulnerability is partly due to /etc/X11/Xsession.d/35x11-common_xhost-local introduced in x11-common in 1:7.6+9 (wheezy and up)
https://lists.debian.org/debian-lts/2016/01/msg00029.html
Upstream announce: http://www.openssh.com/txt/release-7.2

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