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Home >> Browse Vulnerability Assessment Database >> Debian Local Security Checks >> [DSA380] DSA-380-1 xfree86


Vulnerability Assessment Details

[DSA380] DSA-380-1 xfree86

Vulnerability Assessment Summary
DSA-380-1 xfree86

Detailed Explanation for this Vulnerability Assessment

Four vulnerabilities have been discovered in XFree86.
The xterm package provides a terminal escape sequence that reports
the window title by injecting it into the input buffer of the
terminal window, as if the user had typed it. A possible hacker can craft
an escape sequence that sets the title of a victim's xterm window to
an arbitrary string (such as a shell command) and then reports that
title. If the victim is at a shell prompt when this is done, the
injected command will appear on the command line, ready to be run.
Since it is not possible to embed a carriage return in the window
title, the attacker would have to convince the victim to press Enter
(or rely upon the victim's careless or confusion) for the shell or
other interactive process to interpret the window title as user
input. It is conceivable that the attacker could craft other escape
sequences that might convince the victim to accept the injected
input, however. The Common Vulnerabilities and Exposures project at
cve.mitre.org has assigned the name
CVE-2003-0063
to this issue.
To acertain whether your version of xterm is vulnerable to abuse of
the window title reporting feature, run the following command at a
shell prompt from within an xterm window:
(The terminal bell may ring, and the window title may be prefixed
with an "l".)
This flaw is exploitable by anything that can send output to a
terminal window, such as a text document. The xterm user has to
take action to cause the escape sequence to be sent, however (such
as by viewing a malicious text document with the "cat" command).
Whether you are likely to be exposed to it depends on how you use
xterm. Consider the following:
Debian has resolved this problem by disabling the window title
reporting escape sequence in xterm
it is understood but ignored.
The escape sequence to set the window title has not been disabled.
A future release of the xterm package will have a configuration
option to permit the user to turn the window title reporting feature
back on, but it will default off.
The xterm package, since it emulates DEC VT-series text terminals,
emulates a feature of DEC VT terminals known as "User-Defined Keys"
(UDK for short). There is a bug in xterm's handling of DEC UDK
escape sequences, however, and an ill-formed one can cause the xterm
process to enter a tight loop. This causes the process to "spin",
consuming CPU cycles uselessly, and refusing to handle signals (such
as efforts to kill the process or close the window).
To acertain whether your version of xterm is vulnerable to this
attack, run the following command at a shell prompt from within a
"sacrificial" xterm window (i.e., one that doesn't have anything in
the scrollback buffer you might need to see later):
This flaw is exploitable by anything that can send output to a
terminal window, such as a text document. The xterm user has to
take action to cause the escape sequence to be sent, however (such
as by viewing a malicious text document with the "cat" command).
Whether you
[...]

Solution : http://www.debian.org/security/2003/dsa-380
Network Security Threat Level: High

Networks Security ID: 4396, 6940, 6950, 8514

Vulnerability Assessment Copyright: This script is (C) 2005 Michel Arboi

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