Advisory Details

July 15th, 2021

Microsoft Windows CLDFLT Integer Underflow Privilege Escalation Vulnerability

ZDI-21-797
ZDI-CAN-13282

CVE ID CVE-2021-31969
CVSS SCORE 8.8, (AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H)
AFFECTED VENDORS Microsoft
AFFECTED PRODUCTS Windows
VULNERABILITY DETAILS

This vulnerability allows local attackers to escalate privileges on affected installations of Microsoft Windows. 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 cldflt.sys driver. 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 SYSTEM.

ADDITIONAL DETAILS Microsoft has issued an update to correct this vulnerability. More details can be found at:
https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2021-31969
DISCLOSURE TIMELINE
  • 2021-03-10 - Vulnerability reported to vendor
  • 2021-07-15 - Coordinated public release of advisory
CREDIT Anonymous
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