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OpenSSH, Dropbear: Insecure use of system() call


1.  Gentoo Linux Security Advisory

Version Information

Advisory Reference GLSA 200602-11 / OpenSSH
Release Date February 20, 2006
Latest Revision February 20, 2006: 01
Impact low
Exploitable local
Package Vulnerable versions Unaffected versions Architecture(s)
net-misc/openssh < 4.2_p1-r1 >= 4.2_p1-r1 All supported architectures
net-misc/dropbear < 0.47-r1 >= 0.47-r1 All supported architectures

Related bugreports: #119232


A flaw in OpenSSH and Dropbear allows local users to elevate their privileges via scp.

2.  Impact Information


OpenSSH is a free application suite consisting of server and clients that replace tools like telnet, rlogin, rcp and ftp with more secure versions offering additional functionality. Dropbear is an SSH server and client designed with a small memory footprint that includes OpenSSH scp code.


To copy from a local filesystem to another local filesystem, scp constructs a command line using 'cp' which is then executed via system(). Josh Bressers discovered that special characters are not escaped by scp, but are simply passed to the shell.


By tricking other users or applications to use scp on maliciously crafted filenames, a local attacker user can execute arbitrary commands with the rights of the user running scp.

3.  Resolution Information


There is no known workaround at this time.


All OpenSSH users should upgrade to the latest version:

Code Listing 3.1: Resolution

# emerge --sync
# emerge --ask --oneshot --verbose ">=net-misc/openssh-4.2_p1-r1"

All Dropbear users should upgrade to the latest version:

Code Listing 3.2: Resolution

# emerge --sync
# emerge --ask --oneshot --verbose ">=net-misc/dropbear-0.47-r1"

4.  References


Page updated February 20, 2006

Summary: This is a Gentoo Linux Security Advisory

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