FreeBSD VuXML: Documenting security issues in FreeBSD and the FreeBSD Ports Collection

xorg-server -- Information leak in the XkbSetGeometry request of X servers.

Affected packages
xorg-server < 1.14.7_2,1
1.15.0,1 <= xorg-server < 1.16.4,1


VuXML ID 54a69cf7-b2ef-11e4-b1f1-bcaec565249c
Discovery 2015-02-10
Entry 2015-02-12

Peter Hutterer reports:

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.


CVE Name CVE-2015-0255