Debian Security Advisory

DLA-1500-2 openssh -- LTS security update

Date Reported:
12 Sep 2018
Affected Packages:
Security database references:
In the Debian bugtracking system: Bug 908652.
More information:

The security update of OpenSSH announced as DLA 1500-1 introduced a bug in openssh-client: when X11 forwarding is enabled (via system-wide configuration in ssh_config or via -X command line switch), but no DISPLAY is set, the client produces a "DISPLAY "(null)" invalid; disabling X11 forwarding" warning. These bug was introduced by the patch set to fix the CVE-2016-1908 issue. For reference, the following is the relevant section of the original announcement:

  • CVE-2016-1908

    OpenSSH mishandled untrusted X11 forwarding when the X server disables the SECURITY extension. Untrusted connections could obtain trusted X11 forwarding privileges. Reported by Thomas Hoger.

For Debian 8 Jessie, this problem has been fixed in version 1:6.7p1-5+deb8u7.

We recommend that you upgrade your openssh packages.

Further information about Debian LTS security advisories, how to apply these updates to your system and frequently asked questions can be found at: