Advisory Details

December 21st, 2021

X.Org Server SProcRenderCompositeGlyphs Out-Of-Bounds Access Privilege Escalation Vulnerability

ZDI-21-1547
ZDI-CAN-14192

CVE ID CVE-2021-4008
CVSS SCORE 7.8, AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
AFFECTED VENDORS X.Org
AFFECTED PRODUCTS Server
VULNERABILITY DETAILS

This vulnerability allows local attackers to escalate privileges on affected installations of X.Org Server. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability.

The specific flaw exists within the handling of SProcRenderCompositeGlyphs requests. The issue results from the lack of proper validation of user-supplied data, which can result in a memory access past the end of an allocated buffer. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of root.

ADDITIONAL DETAILS X.Org has issued an update to correct this vulnerability. More details can be found at:
https://lists.x.org/archives/xorg-announce/2021-December/003122.html
DISCLOSURE TIMELINE
  • 2021-07-28 - Vulnerability reported to vendor
  • 2021-12-21 - Coordinated public release of advisory
CREDIT Jan-Niklas Sohn
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