AnyDesk Screen Recording Link Following DoS

Executive Summary

CVE-2026-15681 is a denial-of-service vulnerability in AnyDesk software. It allows local attackers who have already gained low-privileged code execution on a target system to create a denial-of-service condition.

The vulnerability exists in how AnyDesk handles screen recording files. An attacker can exploit this flaw by creating a junction (a type of symbolic link in Windows), which tricks the service into creating arbitrary files. This manipulation can lead to system instability or a denial-of-service condition.

• Attackers must first obtain low-privileged code execution on the target system to exploit this vulnerability.
• The flaw involves improper handling of screen recording files, allowing arbitrary file creation via junction manipulation.
• The impact is limited to creating a denial-of-service condition, meaning the system may become unstable or unresponsive.

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Detection Guidance

Detecting this vulnerability requires checking for signs of junction manipulation or unusual file creation by the AnyDesk service. Since the vulnerability involves local exploitation, focus on the target system where AnyDesk is installed.

• Check for unexpected or suspicious junctions in directories where AnyDesk stores screen recording files. Use the following command to list junctions on Windows: 'dir /AL /S C:\'.
• Monitor for unusual file creation or modification in AnyDesk's working directories. Use Windows Event Viewer or tools like Process Monitor to track file system activity related to AnyDesk.
• Verify the integrity of AnyDesk's installation by checking for unexpected files or changes in its default directories. Compare the current installation with a known good baseline.

Since the vulnerability requires low-privileged code execution, ensure no unauthorized processes are running under the context of the affected user. Use commands like 'tasklist' or 'wmic process list' to inspect running processes.

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Impact Analysis

If you use AnyDesk on a system where an attacker has already gained low-privileged access, this vulnerability could impact you in the following ways:

• System instability or crashes: The attacker could cause your system to become unresponsive or crash, disrupting your work or operations.
• Denial-of-service condition: The attacker could prevent you from using AnyDesk or other system functions normally, leading to downtime.
• Potential for further exploitation: While this vulnerability itself does not allow privilege escalation or data theft, it could be combined with other exploits to cause more severe damage.

The impact is primarily limited to availability, meaning the attacker cannot directly steal data or gain higher privileges, but they can disrupt your system's normal operation.

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Compliance Impact

This vulnerability could indirectly affect compliance with standards and regulations like GDPR or HIPAA, depending on the context in which AnyDesk is used. Below are potential compliance considerations:

• GDPR: If AnyDesk is used to handle personal data of EU citizens, a denial-of-service attack could disrupt access to that data, potentially violating GDPR's availability requirements. However, this vulnerability alone does not directly lead to unauthorized data access or disclosure.
• HIPAA: For organizations handling protected health information (PHI), system downtime caused by this vulnerability could disrupt access to critical healthcare systems. HIPAA requires ensuring the availability of PHI, so prolonged denial-of-service conditions might violate this requirement.
• General security standards (e.g., ISO 27001, NIST): This vulnerability could be seen as a failure to maintain system integrity and availability, which are key requirements in these frameworks. Organizations may need to address it as part of their risk management processes.

While the vulnerability does not directly cause data breaches or unauthorized access, its impact on system availability could still pose compliance risks, especially in regulated industries.

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Mitigation Strategies

The primary recommended mitigation is to restrict interaction with the affected AnyDesk product to prevent exploitation.

• Limit user permissions to reduce the risk of low-privileged code execution. Ensure users do not have unnecessary write access to directories used by AnyDesk.
• Monitor and audit AnyDesk's file system activity for signs of junction manipulation or arbitrary file creation. Use logging tools to track suspicious behavior.
• Consider disabling or uninstalling AnyDesk if it is not critical to operations, especially in environments where screen recording features are not required.
• Apply any available patches or updates from AnyDesk as soon as they are released. Check the vendor's official channels for security advisories.

Since the vendor initially deemed the issue out of scope, there may not be an official patch. In such cases, implement compensating controls like network segmentation or endpoint protection to limit the impact of potential exploitation.

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