Hacking

Microsoft warns of a new unpatched Windows Print Spooler RCE zero-day

Microsoft is warning of another zero-day Windows print spooler vulnerability, tracked as CVE-2021-36958, that could allow local attackers to gain SYSTEM privileges.

Microsoft published a security advisory to warn its customers of another remote code execution zero-vulnerability, tracked as CVE-2021-36958, that resides in the Windows Print Spooler component. A local attacker could exploit the vulnerability to gain SYSTEM privileges on vulnerable systems.

“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.” reads the security advisory published by Microsoft. “The workaround for this vulnerability is stopping and disabling the Print Spooler service.”

The flaw received a CVSS score of 7.3, Microsoft said that the only workaround for this issue is to disable the Print Spooler service. The vulnerability was discovered in December by Victor Mata from Accenture Security.

The CERT Coordination Center also recommends blocking outbound SMB traffic to prevent connecting to a malicious shared printer.

“Public exploits for this vulnerability utilize SMB for connectivity to a malicious shared printer. If outbound connections to SMB resources are blocked, then this vulnerability may be mitigated for malicious SMB printers that are hosted outside of your network. Note that Microsoft indicates that printers can be shared via the [MS-WPRN] Web Point-and-Print Protocol, which may allow installation of arbitrary printer drivers without relying on SMB traffic.” reads the security advisory published by CERT Coordination Center . “Also, an attacker local to your network would be able to share a printer via SMB, which would be unaffected by any outbound SMB traffic rules.”

The is the last flaw of a series of bugs in the printer service collectively tracked as PrintNightmare.

In order to address these kinds of flaws, Microsoft implemented the same changes to the default Point and Print default behavior. Non-administrator users will no longer be able to do the following using Point and Print without an elevation of privilege to administrator:

  • Install new printers using drivers on a remote computer or server
  • Update existing printer drivers using drivers from remote computer or server

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Pierluigi Paganini

(SecurityAffairs – hacking, Windows)

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Pierluigi Paganini

Pierluigi Paganini is member of the ENISA (European Union Agency for Network and Information Security) Threat Landscape Stakeholder Group and Cyber G7 Group, he is also a Security Evangelist, Security Analyst and Freelance Writer. Editor-in-Chief at "Cyber Defense Magazine", Pierluigi is a cyber security expert with over 20 years experience in the field, he is Certified Ethical Hacker at EC Council in London. The passion for writing and a strong belief that security is founded on sharing and awareness led Pierluigi to find the security blog "Security Affairs" recently named a Top National Security Resource for US. Pierluigi is a member of the "The Hacker News" team and he is a writer for some major publications in the field such as Cyber War Zone, ICTTF, Infosec Island, Infosec Institute, The Hacker News Magazine and for many other Security magazines. Author of the Books "The Deep Dark Web" and “Digital Virtual Currency and Bitcoin”.

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