The rxvt terminal emulator 2.7.8 and earlier allows attackers to modify the window title via a certain character escape sequence and then insert it back to the command line in the user's terminal, e.g. when the user views a file containing the malicious sequence, which could allow the attacker to execute arbitrary commands.

Digital Defense Inc. released a paper detailing insecurities in various terminal emulators, including rxvt. Many of the features supported by these programs can be abused when untrusted data is displayed on the screen. This abuse can be anything from garbage data being displayed to the screen or a system compromise.

A vulnerability was discovered by Simon Kelley in the dhcpcd DHCP client daemon. dhcpcd has the ability to execute an external script named dhcpcd-<interface>.exe when an IP address is assigned to that network interface. The script sources the file /var/lib/dhcpcd/dhcpcd-<interface>.info which contains shell variables and DHCP assignment information. The way quotes are handled inside these assignments is flawed, and a malicious DHCP server can execute arbitrary shell commands on the vulnerable DHCP client system. This can also be exploited by an attacker able to spoof DHCP responses.

Mandrake Linux packages contain a sample /etc/dhcpc/dhcpcd.exe file and encourages all users to upgrade immediately. Please note that when you do upgrade, you will have to restart the network for the changes to take proper effect by issuing 'service network restart' as root.

Updated rxvt packages are available which fix a number of vulnerabilities in the handling of escape sequences.

[Updated 12 March 2003] Added packages for Red Hat Enterprise Linux ES and Red Hat Enterprise Linux WS

Rxvt is a color VT102 terminal emulator for the X Window System. A number of issues have been found in the escape sequence handling of Rxvt. These could be potentially exploited if an attacker can cause carefully crafted escape sequences to be displayed on an rxvt terminal being used by their victim.

One of the features which most terminal emulators support is the ability for the shell to set the title of the window using an escape sequence. Certain xterm variants, including rxvt, also provide an escape sequence for reporting the current window title. This essentially takes the current title and places it directly on the command line. Since it is not possible to embed a carriage return into the window title itself, the attacker would have to convince the victim to press the Enter key for the title to be processed as a command, although the attacker can perform a number of actions to increase the likelihood of this happening.

A certain escape sequence when displayed in rxvt will create an arbitrary file.

It is possible to add malicious items to the dynamic menus through an escape sequence.

Users of Rxvt are advised to upgrade to these errata packages which contain a patch to disable the title reporting functionality and patches to correct the other issues.

Red Hat would like to thank H D Moore for bringing these issues to our attention.

ID	Name	Product	Family	Severity
14018	Mandrake Linux Security Advisory : rxvt (MDKSA-2003:034)	Nessus	Mandriva Local Security Checks	high
13988	Mandrake Linux Security Advisory : dhcpcd (MDKSA-2003:003)	Nessus	Mandriva Local Security Checks	high
12365	RHEL 2.1 : rxvt (RHSA-2003:055)	Nessus	Red Hat Local Security Checks	high

Detections

Analytics

CVE-2003-0066

critical

Tenable Plugins

high

high

high