X.Org Server XChangeFeedbackControl Integer Underflow Privilege Escalation Vulnerability

April 22nd, 2021
ZDI-21-463 ZDI-CAN-12549

CVE ID

CVE-2021-3472

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 XChangeFeedbackControl requests. The issue results from the lack of proper validation of user-supplied data, which can result in an integer underflow before writing to memory. 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-April/003080.html

Disclosure Timeline

  • 2020-12-16 - Vulnerability reported to vendor
  • 2021-04-22 - Coordinated public release of advisory

Credit

Jan-Niklas Sohn

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