XFree86 Font Information File Buffer Overflow — GLSA 200402-02 Exploitation of a buffer overflow in the XFree86 Project Inc.'s XFree86 X Window System allows local attackers to gain root privileges. Affected packages Package x11-base/xfree on all architectures Affected versions < 4.3.99.902-r1 Unaffected versions = 4.2.1-r3 = 4.3.0-r4 >= 4.3.99.902-r1 Background XFree86, provides a client/server interface between display hardware and the desktop environment while also providing both the windowing infrastructure and a standardized API. XFree86 is platform independent, network-transparent and extensible. Description Exploitation of a buffer overflow in The XFree86 Window System discovered by iDefence allows local attackers to gain root privileges. The problem exists in the parsing of the 'font.alias' file. The X server (running as root) fails to check the length of the user provided input, so a malicious user may craft a malformed 'font.alias' file causing a buffer overflow upon parsing, eventually leading to the execution of arbitrary code. To reproduce the overflow on the command line one can run: # cat > fonts.dir < fonts.alias # X :0 -fp $PWD {Some output removed}... Server aborting... Segmentation fault (core dumped) Impact Successful exploitation can lead to a root compromise provided that the attacker is able to execute commands in the X11 subsystem. This can be done either by having console access to the target or through a remote exploit against any X client program such as a web-browser, mail-reader or game. Workaround No immediate workaround is available; a software upgrade is required. Gentoo has released XFree 4.2.1-r3, 4.3.0-r4 and 4.3.99.902-r1 and encourages all users to upgrade their XFree86 installations. Vulnerable versions are no longer available in Portage. Resolution All users are recommended to upgrade their XFree86 installation: # emerge sync # emerge -pv x11-base/xfree # emerge x11-base/xfree References CVE: CAN-2004-0083 Vulnerability: XFree86 Font Information File Buffer Overflow