CVE-2026-39880
Authentication Bypass in Remnawave Backend Allows Device Limit Evasion
Publication date: 2026-04-08
Last updated on: 2026-04-17
Assigner: GitHub, Inc.
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| remnawave | remnawave_backend | to 2.7.4 (inc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-362 | The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
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.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
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.
How can this vulnerability impact me? :
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.
How can this vulnerability be detected on my network or system? Can you suggest some commands?
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.
What immediate steps should I take to mitigate this vulnerability?
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.