In the ever-evolving landscape of cybersecurity threats, attackers continuously find new vulnerabilities to exploit. One such critical vulnerability recently discovered is CVE-2025-0411, a flaw in the popular file archiving tool, 7-Zip. This flaw, which allows attackers to bypass Windows Mark-of-the-Web (MotW) protections, has been actively exploited in the wild by Russian cybercrime groups. Their primary target? Government and non-governmental organizations in Ukraine, amidst the backdrop of the ongoing Russo-Ukrainian conflict.
Understanding the 7-Zip Flaw (CVE-2025-0411)
The CVE-2025-0411 vulnerability received a CVSS score of 7.0, indicating a high level of severity. This flaw allows remote attackers to execute arbitrary code within the context of the current user. The attack vector primarily involves phishing emails containing maliciously crafted archives designed to exploit this vulnerability.
7-Zip, a widely used open-source file archiver, patched this flaw in version 24.09, released in November 2024. However, before the patch, threat actors actively exploited the vulnerability, taking advantage of its ability to bypass MotW protections.
Mark-of-the-Web (MotW) is a critical security feature in Windows, designed to flag files downloaded from the internet. This flag prompts additional security checks before the file is executed. CVE-2025-0411 effectively bypasses this safeguard by exploiting how 7-Zip handles double-archived content.
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How Does the Exploit Work?
The root cause of the vulnerability lies in the improper propagation of MotW protections in double-encapsulated archives. In simple terms, if an attacker creates an archive, then compresses that archive into another archive, the MotW protections do not apply to the files inside.
Here’s a breakdown of the attack sequence:
- Phishing Email:
Attackers send phishing emails from compromised Ukrainian government or business accounts, making them appear legitimate. - Homoglyph Attack:
The email contains a malicious archive file with a homoglyph attack—a method where visually similar characters are used to spoof file extensions (e.g., using Cyrillic ‘а’ instead of Latin ‘a’ in “.docx” to trick users). - Double Archive Exploit:
The archive contains another ZIP file disguised as a Microsoft Word document. When opened, it triggers the CVE-2025-0411 vulnerability. - Malicious Payload:
This leads to the execution of an internet shortcut (.URL) file within the archive, which connects to an attacker-controlled server to download another ZIP file. - SmokeLoader Deployment:
The downloaded ZIP contains SmokeLoader malware, disguised as a harmless PDF document. SmokeLoader is known for its ability to download and install additional malicious payloads on infected systems.
SmokeLoader Malware: A Closer Look
SmokeLoader, first identified in 2011, is a modular malware loader primarily used to distribute other types of malware, such as banking trojans, ransomware, and information stealers. Its adaptability and stealth have made it a favorite tool among cybercriminal groups.
In the context of the CVE-2025-0411 exploit, SmokeLoader has been used to:
- Establish persistence on infected systems.
- Exfiltrate sensitive data from targeted organizations.
- Deploy additional malware to expand the attack footprint.
- Act as a backdoor for future cyber-espionage activities.
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Targets and Impact of the Campaign
Trend Micro’s investigation revealed that at least nine Ukrainian government entities and other organizations were impacted, including:
- Ministry of Justice of Ukraine
- Kyiv Public Transportation Service
- Kyiv Water Supply Company
- Kyiv City Council
Interestingly, the attackers didn’t limit their focus to large government bodies. Smaller municipal organizations were also targeted, likely because these entities often lack the robust cybersecurity infrastructure of their larger counterparts. This makes them ideal pivot points for attackers to infiltrate larger networks.
Why Smaller Organizations Are Vulnerable
Peter Girnus, a Trend Micro security researcher, pointed out a significant observation:
“These smaller organizations are often under intense cyber pressure yet are overlooked, less cyber-savvy, and lack resources for comprehensive cyber strategies.”
This vulnerability is not unique to Ukraine. Globally, smaller government and business entities often become entry points for attackers seeking access to more significant, well-protected targets.
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Recommendations for Mitigation
Given the severity and active exploitation of CVE-2025-0411, cybersecurity experts recommend the following actions:
- Update 7-Zip Immediately:
Ensure all systems are updated to 7-Zip version 24.09 or later, where the vulnerability has been patched. - Implement Email Security Measures:
- Use advanced email filtering to detect phishing attempts.
- Block emails with suspicious attachments or homoglyph file names.
- Disable Execution from Untrusted Sources:
Restrict execution of files from untrusted sources, particularly .URL files from downloaded archives. - User Awareness Training:
Educate employees about phishing tactics, homoglyph attacks, and safe handling of email attachments. - Network Segmentation:
Segment critical networks to limit the spread of malware in case of an initial breach. - Enable Advanced Threat Protection:
Utilize endpoint detection and response (EDR) solutions to identify and respond to suspicious activities promptly.
By staying informed about vulnerabilities like CVE-2025-0411 and implementing robust cybersecurity measures, organizations can significantly reduce their risk of falling victim to sophisticated cyber threats.
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Frequently Asked Questions (FAQs):
- What is CVE-2025-0411?
CVE-2025-0411 is a security vulnerability in 7-Zip that allows attackers to bypass Windows Mark-of-the-Web protections and execute malicious code. - How does the 7-Zip flaw affect Windows security?
It allows attackers to execute files without triggering Windows security checks designed for files downloaded from the internet. - What is SmokeLoader malware?
SmokeLoader is a malware loader used to install additional malicious software on infected devices, often used in cyber-espionage campaigns. - How are phishing emails used in this attack?
Attackers send emails with malicious archives disguised as legitimate documents to trick users into opening them, exploiting the 7-Zip flaw. - What is a homoglyph attack?
A homoglyph attack uses visually similar characters to spoof file extensions, tricking users into thinking a file is safe when it’s not. - Who are the primary targets of this cyberattack?
Ukrainian government entities, municipal organizations, and businesses have been the main targets of these phishing campaigns. - How can I protect my system from CVE-2025-0411?
Update to 7-Zip version 24.09, enable advanced email filtering, and avoid opening files from untrusted sources. - When was this vulnerability first exploited?
The first known exploitation of CVE-2025-0411 occurred on September 25, 2024. - What is Mark-of-the-Web (MotW)?
MotW is a Windows security feature that flags files downloaded from the internet, prompting additional security checks before execution. - Why are smaller organizations at greater risk?
They often lack the cybersecurity resources of larger entities, making them vulnerable entry points for attackers targeting bigger networks.