# CVE-2026-45289: CloudburstMC Protocol: Partially missing validation for FULL type authentication tokens

> Attackers can bypass authentication in Minecraft Bedrock Edition servers using this library due to missing validation for FULL type tokens.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 2 Jun 2026
- **Updated:** 3 Jun 2026

## What is CVE-2026-45289?

CVE-2026-45289 is a medium-severity authentication bypass vulnerability in CloudburstMC Protocol, published on 2 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

CloudburstMC Protocol is a protocol library for Minecraft Bedrock Edition. Prior to version 3.0.0.Beta12-20260420.182526-15, CloudburstMC Protocol is partially missing validation for FULL type authentication tokens (Cloudburst/Protocol). This vulnerability impacts publicly accessible software depending on the affected versions of Protocol, specifically the EncryptionUtils methods to validate auth payloads for FULL type tokens. This issue has been patched in version 3.0.0.Beta12-20260420.182526-15.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2026-45289?


## How do I fix CVE-2026-45289?

No fix has been published for CVE-2026-45289 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-45289 being exploited?

There is no known exploitation of CVE-2026-45289 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-45289 and fix it if it is affected.

What it is: CVE-2026-45289 is a medium-severity authentication bypass vulnerability in CloudburstMC Protocol, published on 2 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-45289 in the wild and no public exploit code.

Affected product: CloudburstMC Protocol. 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-2026-45289/ (Markdown: https://insights.sbomify.com/CVE-2026-45289/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-45289
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-45289
- OSV: https://osv.dev/vulnerability/CVE-2026-45289

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-45289/
Summaries are generated and may contain mistakes; the official description above is the record.