# CVE-2018-21031: Auth bypass in n/a

> Remote attackers can bypass access controls in Plex Media Server by retrieving the X-Plex-Token from vulnerable Tautulli instances.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/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:** 18 Nov 2019
- **Updated:** 5 Aug 2024
- **Also known as:** GHSA-9qh9-xp4m-mxph

## What is CVE-2018-21031?

CVE-2018-21031 is a medium-severity authentication bypass vulnerability in n/a, published on 18 Nov 2019. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Tautulli versions 2.1.38 and below allows remote attackers to bypass intended access control in Plex Media Server because the X-Plex-Token is mishandled and can be retrieved from Tautulli. NOTE: Initially, this id was associated with Plex Media Server 1.18.2.2029-36236cc4c as the affected product and version. Further research indicated that Tautulli is the correct affected product.

Weakness: CWE-522 (Insufficiently Protected Credentials)

## Which versions are affected by CVE-2018-21031?

It affects 1 product.


Products: Plex Media Server.

## How do I fix CVE-2018-21031?

No fix has been published for CVE-2018-21031 yet. Limit exposure of the affected software until one is available.

## Is CVE-2018-21031 being exploited?

There is no known exploitation of CVE-2018-21031 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2026-96656](https://insights.sbomify.com/CVE-2026-96656/): Plex Media Server External Control of File Name or Path (high 8.6, exploited in the wild)
- [CVE-2020-5741](https://insights.sbomify.com/CVE-2020-5741/): Plex Media Server Remote Code Execution (high 7.2, exploited in the wild)
- [CVE-2026-96654](https://insights.sbomify.com/CVE-2026-96654/): Plex Media Server Improper Neutralization of Encoded URI Schemes in a Web Page (medium 6.9, exploited in the wild)
- [CVE-2026-96652](https://insights.sbomify.com/CVE-2026-96652/): Plex Media Server Server-Side Request Forgery (SSRF) (medium 5.3, exploited in the wild)
- [CVE-2026-96655](https://insights.sbomify.com/CVE-2026-96655/): Plex Media Server Server-Side Request Forgery (SSRF) (medium 5.3, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-21031 and fix it if it is affected.

What it is: CVE-2018-21031 is a medium-severity authentication bypass vulnerability in n/a, published on 18 Nov 2019. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2018-21031 in the wild and no public exploit code.

Affected product: n/a. 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-2018-21031/ (Markdown: https://insights.sbomify.com/CVE-2018-21031/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-21031
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-21031
- OSV: https://osv.dev/vulnerability/CVE-2018-21031

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-21031/
Summaries are generated and may contain mistakes; the official description above is the record.