Vulnerability can be exploited to turn users into system stars, no patch available yet

A bug-hunter who previously disclosed Windows security flaws has publicly revealed another zero-day vulnerability in Microsoft’s latest operating systems.

The discovered hole can be exploited by malware and rogue logged-in users to gain system-level privileges on Windows 10 and recent Server releases, allowing them to gain full control of the machine. No patch exists for this bug, details and exploit code for which were shared online on Tuesday for anyone to use and abuse.

The flaw was uncovered, and revealed on Microsoft-owned GitHub, funnily enough, by a pseudonymous netizen going by the handle SandboxEscaper. She has previously dropped Windows zero-days that can be exploited to delete or tamper with operating system components, elevate local privileges, and so on.

This latest one works by abusing Windows’ schtasks tool, designed to run programs at scheduled times, along with quirks in the operating system.

Meanwhile… If you haven’t yet patched the wormable RDP security flaw in Windows (CVE-2019-0708), please do so ASAP – exploit code that can crash vulnerable systems is doing the rounds, and McAfee eggheads have developed and described a proof-of-concept attack that executes arbitrary software on remote machines, with no authentication required. Eek.

It appears the exploit code imports a legacy job file into the Windows Task Scheduler using schtasks, creating a new task, and then deletes that new task’s file from the Windows folder. Next, it creates a hard filesystem link pointing from where the new task’s file was created to pci.sys, one of Windows’ kernel-level driver files, and then runs the same schtasks command again. This clobbers pci.sys’s access permissions so that it can be modified and overwritten by the user, thus opening the door to privileged code execution.

The exploit, as implemented, needs to know a valid username and password combo on the machine to proceed, it seems. It can be tweaked and rebuilt from its source code to target other system files, other than pci.sys. …….