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Apple recently fixed a security vulnerability in the macOS operating system that could be potentially exploited by a threat actor to “trivially and reliably” bypass a “myriad of foundational macOS security mechanisms” and run arbitrary code.

Security researcher Patrick Wardle detailed the discovery in a series of tweets on Thursday. Tracked as CVE-2021-30853 (CVSS score: 5.5), the issue relates to a scenario where a rogue macOS app may circumvent Gatekeeper checks, which ensure that only trusted apps can be run and that they have passed an automated process called “app notarization.”

The iPhone maker, crediting Gordon Long of Box with reporting the flaw, said it addressed the weakness with improved checks as part of macOS 11.6 updates officially released on September 20, 2021.

“Such bugs are often particularly impactful to everyday macOS users as they provide a means for adware and malware authors to sidestep macOS security mechanisms, …mechanisms that otherwise would thwart infection attempts,” Wardle said in a technical write-up of the flaw.

Specifically, the bug not only gets around Gatekeeper, but also File Quarantine and macOS’s notarization requirements, effectively allowing a seemingly innocuous PDF file to compromise the entire system simply by opening it. According to Wardle, the issue is rooted in the fact that an unsigned, non-notarized script-based application can not explicitly specify an interpreter, resulting in a complete bypass.

images from Hacker News