Advisory Details

May 19th, 2020

(0Day) Microsoft Windows splwow64 Untrusted Pointer Dereference Privilege Escalation Vulnerability

ZDI-20-665
ZDI-CAN-10016

CVE ID CVE-2020-0916
CVSS SCORE 7.0, (AV:L/AC:H/PR:L/UI:N/S:U/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 user-mode printer driver host process splwow64.exe. The issue results from the lack of proper validation of a user-supplied value prior to dereferencing it as a pointer. An attacker can leverage this vulnerability to escalate privileges from low integrity and execute code in the context of the current user at medium integrity.

ADDITIONAL DETAILS

This vulnerability is being disclosed publicly without a patch in accordance with ZDI policies.

12/26/20 – ZDI sent the vulnerability report to the vendor and the vendor acknowledged
12/27/20 – The vendor provided a case ID and requested additional evidence
04/01/20 – The vendor requested an extension from 04/24/20 to 05/12/20 and ZDI agreed
05/07/20 – The vendor notified ZDI they would miss the 05/12/20 patch date, but did offer a beta for testing
05/08/20 – ZDI agreed to test
05/12/20 – ZDI confirmed the beta patch succeeded, but also communicated the intent to publish the reports as 0-day as extension options are expired

-- Mitigation:
Given the nature of the vulnerability, the only salient mitigation strategy is to restrict interaction with the service. Only the clients and servers that have a legitimate procedural relationship with the service should be permitted to communicate with it.


DISCLOSURE TIMELINE
  • 2019-12-26 - Vulnerability reported to vendor
  • 2020-05-19 - Coordinated public release of advisory
CREDIT Lucas Leong (@_wmliang_) of Trend Micro's Zero Day Initiative
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