# CVE-2026-39880: Remnawave Backend has a race condition in HWID device limit allows bypassing max devices

> Authenticated users can bypass HWID device limits via a race condition, enabling subscription resale and excessive traffic consumption.

- **Severity:** Medium 5.0 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 8 Apr 2026
- **Updated:** 10 Apr 2026
- **Also known as:** GHSA-985p-44h5-v3pq

## What is CVE-2026-39880?

CVE-2026-39880 is a medium-severity vulnerability in remnawave backend, published on 8 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Remnawave Backend is the backend for the Remnawave proxy and user management solution. Prior to 2.7.5, a glitch in the HWID device registration logic allows an authenticated user to bypass the configured limit for HWID devices and register more devices than expected, allowing them to resell subscriptions and consume excessive traffic. This vulnerability is fixed in 2.7.5.

Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2026-39880?

It affects 1 product.


Products: Remnawave Remnawave Backend.

## How do I fix CVE-2026-39880?

No fix has been published for CVE-2026-39880 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-39880 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39880 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-39880 and fix it if it is affected.

What it is: CVE-2026-39880 is a medium-severity vulnerability in remnawave backend, published on 8 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39880 exists.

Affected product: remnawave backend. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-39880/ (Markdown: https://insights.sbomify.com/CVE-2026-39880/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-39880
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-39880
- OSV: https://osv.dev/vulnerability/CVE-2026-39880

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-39880/
Summaries are generated and may contain mistakes; the official description above is the record.