CVE-2018-14598

It was discovered that libX11 does not properly validate input coming from the server, causing XListExtensions() and XGetFontPath() functions to produce an invalid list of elements that in turn make XFreeExtensionsList() and XFreeFontPath() access invalid memory. An attacker who can either configure a malicious X server or modify the data coming from one, could use this flaw to crash the application using libX11, resulting in a denial of service.

This issue did not affect the versions of libX11 as shipped with Red Hat Enterprise Linux 5 as they did not include the vulnerable code.

To exploit the vulnerability an attacker would need to have already compromised the X server used by your applications. Normally, the X client that runs libX11 and the X server runs on the same machine, thus if an attacker can trigger this flaw he has already compromised the X server, which runs as root, and he has already full control on the system. If the X client runs on another system than the X server (e.g. DISPLAY environment variable is used and it points to an X server on another system) then exploiting this vulnerability would only crash the client, which should not be run with high privileges. For the above reasons, this flaw was rated as Moderate Impact.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.