Compliance Impact

The vulnerability allows authenticated users to bypass device registration limits, leading to excessive resource consumption and potential unauthorized reselling of subscriptions.

While the CVE description does not explicitly mention compliance with standards like GDPR or HIPAA, the ability to circumvent device limits and resell subscriptions could indirectly impact compliance by undermining access controls and resource management policies.

However, there is no direct information provided about data confidentiality breaches or personal data exposure that would clearly affect GDPR or HIPAA compliance.

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Executive Summary

CVE-2026-39880 is a race condition vulnerability in the HWID (Hardware ID) device registration logic of the Remnawave Backend, affecting versions prior to 2.7.5.

The flaw occurs because the code that enforces the maximum allowed HWID devices per user does not use atomic operations or transactional locking. This means multiple concurrent requests can bypass the device limit by simultaneously checking the current number of registered devices before any new registrations are committed.

As a result, an authenticated user can register more devices than the configured limit, enabling them to resell subscriptions and consume excessive traffic.

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Impact Analysis

This vulnerability allows authenticated users to bypass device registration limits, which can lead to several negative impacts:

• Service owners lose control over device limits, resulting in increased resource consumption and traffic.
• Abusive users can register more devices than allowed, potentially reselling subscriptions.
• Legitimate customers and resellers may be disadvantaged due to resource abuse by others.

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Detection Guidance

This vulnerability can be detected by monitoring for multiple concurrent device registration requests from the same authenticated user that exceed the configured HWID device limit.

A practical detection method involves intercepting and analyzing device registration requests to identify if multiple registrations are occurring simultaneously, bypassing the device limit.

For example, you can use network traffic analysis tools or proxy logs to detect repeated or concurrent POST/GET requests to the device registration endpoint.

While no specific commands are provided, you might use tools like tcpdump, Wireshark, or HTTP proxy logs to capture and analyze these requests.

Additionally, scripting with curl or similar tools to simulate concurrent device registration requests can help verify if the system is vulnerable.

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Mitigation Strategies

The immediate mitigation step is to upgrade the Remnawave Backend to version 2.7.5 or later, where this race condition vulnerability has been fixed.

Until the upgrade can be applied, consider implementing transactional locking or atomic operations around the HWID device registration logic to prevent concurrent requests from bypassing device limits.

Monitoring and rate-limiting device registration requests per user can also help reduce the risk of exploitation.

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