The menace actor often known as EncryptHub exploited a recently-patched safety vulnerability in Microsoft Home windows as a zero-day to ship a variety of malware households, together with backdoors and knowledge stealers corresponding to Rhadamanthys and StealC.
“On this assault, the menace actor manipulates .msc information and the Multilingual Consumer Interface Path (MUIPath) to obtain and execute malicious payload, preserve persistence and steal delicate information from contaminated programs,” 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 would permit an attacker to bypass a safety function regionally. It was mounted 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 beneath the title Water Gamayun. The menace actor, not too long ago the topic of analyses by PRODAFT and Outpost24, can also be referred to as LARVA-208.
CVE-2025-26633, at its core, leverages the Microsoft Administration Console framework (MMC) to execute a malicious Microsoft Console (.msc) file via a PowerShell loader known as MSC EvilTwin loader.
Particularly, it includes the loader creating two .msc information with the identical title: 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 a substitute and executes it. That is achieved by exploiting MMC’s Multilingual Consumer Interface Path (MUIPath) function.
“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 a substitute 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 information –
- 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 corresponding to “C:Home windows System32” (word the house after Home windows) to bypass Consumer Account Management (UAC) and drop a malicious .msc file referred to as “WmiMgmt.msc”
Development Micro stated the assault chains doubtless start with victims downloading digitally-signed Microsoft installer (MSI) information 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 menace actor has been experimenting with these strategies since April 2024.
“This marketing campaign is beneath lively growth; it employs a number of supply strategies and customized payloads designed to keep up persistence and steal delicate information, then exfiltrate it to the attackers’ command-and-control (C&C) servers,” Zahravi stated.
