High
CVE-2021-34481
CVE-2021-34481
Description
A remote code execution vulnerability exists when the Windows Print Spooler service improperly performs privileged file operations. An attacker who successfully exploited this vulnerability could run arbitrary code with SYSTEM privileges. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.
UPDATE August 10, 2021: Microsoft has completed the investigation and has released security updates to address this vulnerability. Please see the Security Updates table for the applicable update for your system. We recommend that you install these updates immediately. This security update changes the Point and Print default behavior; please see KB5005652.
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Technical Analysis
CVE-2021-34481 was the result of two features intended to make the standard (non-administrative) Windows user’s life easier:
- Adding a remote printer did not require administrative access. Just point your computer at the remote printer and print.
- Adding a printer whose drivers were in the driver store did not require administrative access.
These two mechanisms combined allowed a low privileged Windows user to add arbitrary signed drivers to the driver store and then install them at will. A low privileged user could install a vulnerable print driver and exploit it to achieve SYSTEM privileges. In the DEF CON 29 talk Bring Your Own Vulnerable Print Driver, the example vulnerable drivers were Lexmark Universal Print Driver (CVE-2021-35449) , Canon TR150 Print Driver (CVE-2021-38085), and Ricoh PCL6 Print Driver (CVE-2019-19363).
Microsoft patched this issue by, essentially, removing the ability for a low privileged user to easily install a remote printer.
An exploit with some additional details was posted on GitHub.
CVSS V3 Severity and Metrics
General Information
Vendors
- microsoft
Products
- windows 10 -,
- windows 10 1607,
- windows 10 1809,
- windows 10 1909,
- windows 10 2004,
- windows 10 20h2,
- windows 10 21h1,
- windows 7 -,
- windows 8.1 -,
- windows rt 8.1 -,
- windows server 2008 -,
- windows server 2008 r2,
- windows server 2012 -,
- windows server 2016 -,
- windows server 2016 2004,
- windows server 2019 -
