Arch Linux Security Advisory ASA-201502-11
=========================================
Severity: Medium
Date    : 2015-02-10
CVE-ID  : CVE-2015-0245
Package : xorg-server
Type    : information leak, denial of service
Remote  : Yes
Link    : https://wiki.archlinux.org/title/CVE

Summary
======
The package xorg-server before version 1.16.4-1 is vulnerable to
information leak and denial of service.

Resolution
=========
Upgrade to 1.16.4-1.

# pacman -Syu "xorg-server>=1.16.4-1"

The problem has been fixed upstream in version 1.16.4.

Workaround
=========
None.

Description
==========
Olivier Fourdan from Red Hat has discovered a protocol handling issue in
the way the X server code base handles the XkbSetGeometry request.

The issue stems from the server trusting the client to send valid string
lengths in the request data. A malicious client with string lengths
exceeding the request length can cause the server to copy adjacent
memory data into the XKB structs. This data is then available to the
client via the XkbGetGeometry request.
The data length is at least up to 64k, it is possible to obtain more
data by chaining strings, each string length is then determined by
whatever happens to be in that 16-bit region of memory.

A similarly crafted request can likely cause the X server to crash.

Impact
=====
A remote attacker is able to use specially crafted XkbSetGeometry
requests to obtain adjacent memory data into the XKB structs leading to
information leakage or cause the X server to crash resulting in denial
of service.

References
=========
https://www.x.org/wiki/Development/Security/Advisory-2015-02-10/
https://cgit.freedesktop.org/xorg/xserver/commit/
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-0255