EncryptHub Exploits Windows Zero-Day Vulnerability: What You Need to Know

A new cyber threat has emerged, with the notorious hacking group EncryptHub exploiting a critical Windows vulnerability before it was patched by Microsoft. The flaw, tracked as CVE-2025-26633, resides in the Microsoft Management Console (MMC) and allows attackers to bypass security warnings and execute malicious code. Security researchers at Trend Micro uncovered this zero-day attack, which has been actively used to steal sensitive data and deploy ransomware.

This revelation highlights the ongoing battle between cybercriminals and security professionals, emphasizing the need for immediate system updates and enhanced security measures. Let’s break down what this vulnerability is, how EncryptHub has exploited it, and what it means for cybersecurity.

EncryptHub’s Zero-Day Exploit: A Breakdown

• The Vulnerability: CVE-2025-26633, also known as MSC EvilTwin, is a Windows security feature bypass vulnerability that allows attackers to execute malicious code without user warnings.
• How It Works: The flaw exists in how MSC (Microsoft Management Console) files are processed. Attackers use this to evade Windows file reputation checks and launch malware.

– Exploitation Methods:

• Email Attacks: Hackers send malicious MSC files to unsuspecting users, tricking them into opening the file.
• Web-Based Attacks: The files are hosted on attacker-controlled or compromised websites, waiting for users to access them.
• Who’s Behind It? EncryptHub, also known as Water Gamayun or Larva-208, is responsible for this attack. They have a history of using zero-day vulnerabilities to steal data.

– Malware Used:

– EncryptHub Stealer

– DarkWisp & SilentPrism backdoors

– Stealc & Rhadamanthys stealer

– PowerShell-based MSC EvilTwin trojan loader

• Attack Timeline: Trend Micro found evidence of this technique being tested as early as April 2024.
• Targeted Organizations: EncryptHub has breached at least 618 organizations globally, using spear-phishing and social engineering tactics.
• Ransomware Deployment: EncryptHub works as an affiliate of RansomHub and BlackSuit ransomware, encrypting victims’ files after stealing sensitive data.

– Microsoft’s Response:

• Released a security patch for CVE-2025-26633 this month.
• Fixed another zero-day vulnerability (CVE-2025-24983) in the Windows Win32 Kernel Subsystem, which had been exploited since March 2023.

What Undercode Say: Analyzing the Attack

EncryptHub’s use of CVE-2025-26633 showcases a growing trend in cybercrime: the rapid exploitation of zero-day vulnerabilities before patches are available. Here’s why this attack is particularly concerning:

1. Zero-Day Exploitation Is Increasing

Zero-day vulnerabilities are being weaponized faster than ever. Attackers are investing heavily in discovering and using unknown flaws before vendors can patch them.

2. Bypassing Security Warnings Is a Game Changer

Unlike traditional malware that triggers security alerts, MSC EvilTwin allows attackers to execute code without Windows warning the user. This makes it highly effective in phishing campaigns.

3. Multi-Layered Attacks Increase Complexity

EncryptHub doesn’t rely on a single method—it combines phishing, backdoors, and ransomware, making detection and mitigation more difficult.

4. Supply Chain Attacks Could Be Next

Given the ability to deliver payloads through websites, EncryptHub could expand into supply chain attacks, compromising legitimate software vendors.

5. The Role of Ransomware in Modern Cybercrime

EncryptHub’s affiliation with RansomHub and BlackSuit ransomware highlights how cybercriminal groups are collaborating. They steal data first, then encrypt files, maximizing their extortion leverage.

6. Microsoft’s Patch Cycle vs. Threat Actors’ Speed

Although Microsoft responded with a patch, EncryptHub was already exploiting the flaw. This shows that organizations cannot rely solely on patches—proactive defenses are necessary.

7. What Can Organizations Do?

• Patch Immediately – Install Microsoft’s update to fix CVE-2025-26633.
• Implement Zero Trust Security – Assume breaches will happen and restrict access.
• Monitor Network Traffic – Detect unusual activity before attackers exfiltrate data.
• User Awareness Training – Educate employees on phishing tactics.
• Advanced Threat Detection – Use AI-based security tools to identify anomalies.

Fact Checker Results:

1. The CVE-2025-26633 vulnerability is real and has been patched by Microsoft.
2. EncryptHub has been linked to ransomware and data theft, confirming its role in recent attacks.
3. Trend Micro’s findings align with previous research, proving that this technique was tested as early as April 2024.

Cybersecurity threats are evolving rapidly, and this case is another reminder of why staying ahead of attackers is critical. Organizations must be proactive, not reactive, in defending against cyber threats.

References:

Reported By: https://www.bleepingcomputer.com/news/security/encrypthub-linked-to-zero-day-attacks-targeting-windows-systems/
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