Colin Mc Hugo

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Colin Mc Hugo
Security Engineer Manager & CEO at Quantum Infinite Solutions Group Ltd.

Microsoft issues patch to fix PrintNightmare zero‑day bug

July 23, 2021

The out-of-band replace fixes a distant code execution flaw affecting the Home windows Print Spooler service

Microsoft on Wednesday launched an emergency replace to plug a vulnerability in  the Home windows Print Spooler service that’s being actively exploited within the wild. Dubbed PrintNightmare, the zero-day security flaw impacts all variations of the Microsoft Home windows working system going again so far as Home windows 7.

Listed as CVE-2021-34527, the remote-code execution bug is ranked excessive in severity and holds a rating of 8.2 of 10 on the Common Vulnerability Scoring System (CVSS) scale. The safety loophole was thought of so extreme that Microsoft determined to concern an out-of-band patch, as an alternative of releasing the repair as a part of its ordinary Patch Tuesday bundle, which is scheduled for subsequent week.

“A distant code execution vulnerability exists when the Home windows Print Spooler service improperly performs privileged file operations. An attacker who efficiently exploited this vulnerability might run arbitrary code with SYSTEM privileges. An attacker might then set up applications; view, change, or delete information; or create new accounts with full consumer rights,” reads Microsoft’s description of the bug.

The latest replace was pushed out to patch variations of Home windows that weren’t addressed within the earlier out-of-band safety replace launched on July sixth; particularly Home windows Server 2012, Home windows Server 2016, and Home windows 10, Model 1607.

Nevertheless, some researchers quickly noted that the patch doesn’t deal with the total extent of the vulnerability. Certainly, the Redmond tech big additionally identified that beneath sure circumstances the techniques will nonetheless be susceptible: “Having NoWarningNoElevationOnInstall set to 1 makes your system susceptible by design.” Nevertheless, it additionally revealed workarounds for the issue.

The primary workaround focuses on disabling the Print Spooler service, which can forestall customers from printing each domestically and remotely. In the meantime, the second instructs admins and customers to disable inbound distant printing by Group Coverage. It will block distant assaults because it prevents inbound distant printing operations, however the system will stop to perform as a print server. Printing by instantly linked gadgets will nonetheless be attainable, although.

The vulnerability may very well be traced again to the tip of June, when a gaggle of safety researchers published a proof-of-concept exploit, mistakenly believing that the problem had been resolved. The confusion stemmed from the same vulnerability (CVE-2021-1675) that additionally impacts the Print Spooler service.

Admins and customers who didn’t get round to patching their techniques would do effectively to take action instantly. The updates might be discovered on all the standard launch channels equivalent to Home windows Replace, Microsoft Replace Catalog, and Home windows Server Replace Providers.

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