The risk actor often known as EncryptHub exploited a recently-patched security vulnerability in Microsoft Home windows as a zero-day to ship a variety of malware households, together with backdoors and knowledge stealers akin to Rhadamanthys and StealC.
“On this assault, the risk actor manipulates .msc recordsdata and the Multilingual Person Interface Path (MUIPath) to obtain and execute malicious payload, keep persistence and steal delicate information from contaminated techniques,” Development Micro researcher Aliakbar Zahravi stated in an evaluation.
The vulnerability in query is CVE-2025-26633 (CVSS rating: 7.0), described by Microsoft as an improper neutralization vulnerability in Microsoft Administration Console (MMC) that might permit an attacker to bypass a security characteristic regionally. It was fastened by the corporate earlier this month as a part of its Patch Tuesday replace.
Development Micro has given the exploit the moniker MSC EvilTwin, monitoring the suspected Russian exercise cluster below the identify Water Gamayun. The risk actor, not too long ago the topic of analyses by PRODAFT and Outpost24, can also be known as LARVA-208.
CVE-2025-26633, at its core, leverages the Microsoft Administration Console framework (MMC) to execute a malicious Microsoft Console (.msc) file by way of a PowerShell loader known as MSC EvilTwin loader.
Particularly, it includes the loader creating two .msc recordsdata with the identical identify: One clear file and its rogue counterpart that’s dropped in the identical location however inside a listing named “en-US.” The thought is that when the previous is run, MMC inadvertently picks the malicious file as an alternative and executes it. That is achieved by exploiting MMC’s Multilingual Person Interface Path (MUIPath) characteristic.
“By abusing the way in which that mmc.exe makes use of MUIPath, the attacker can equip MUIPath en-US with a malicious .msc file, which trigger the mmc.exe load this malicious file as an alternative of the unique file and executed with out the sufferer’s information,” Zahravi defined.
EncryptHub has additionally been noticed adopting two different strategies to run malicious payload on an contaminated system utilizing .msc recordsdata –
- Utilizing the ExecuteShellCommand methodology of MMC to obtain and execute a next-stage payload on the sufferer’s machine, an strategy beforehand documented by Dutch cybersecurity firm Outflank in August 2024
- Utilizing mock trusted directories akin to “C:Home windows System32” (observe the house after Home windows) to bypass Person Account Management (UAC) and drop a malicious .msc file known as “WmiMgmt.msc”
Development Micro stated the assault chains seemingly start with victims downloading digitally-signed Microsoft installer (MSI) recordsdata impersonating official Chinese language software program like DingTalk or QQTalk, which is then used to fetch and execute the loader from a distant server. It is stated that the risk actor has been experimenting with these strategies since April 2024.
“This marketing campaign is below energetic growth; it employs a number of supply strategies and customized payloads designed to take care of persistence and steal delicate information, then exfiltrate it to the attackers’ command-and-control (C&C) servers,” Zahravi stated.
