# CVE-2021-25827: Auth bypass in n/a

> Attackers can bypass authentication by spoofing the X-Forwarded-For header with a local IP address, gaining unauthorized access to the server.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 28 Jun 2023
- **Updated:** 13 Feb 2025
- **Also known as:** GHSA-m4q9-68f2-5wc6

## What is CVE-2021-25827?

CVE-2021-25827 is a critical authentication bypass vulnerability in n/a, published on 28 Jun 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Emby Server < 4.7.12.0 is vulnerable to a login bypass attack by setting the X-Forwarded-For header to a local IP-address.

Weakness: CWE-290 (Authentication Bypass by Spoofing)

## Which versions are affected by CVE-2021-25827?

It affects 1 product.


Products: Emby Emby.

## How do I fix CVE-2021-25827?

No fix has been published for CVE-2021-25827 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-25827 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-25827 exists.

## Other vulnerabilities in n/a

- [CVE-2020-26948](https://insights.sbomify.com/CVE-2020-26948/): Server-side request forgery in n/a (critical 9.8)
- [CVE-2025-64113](https://insights.sbomify.com/CVE-2025-64113/): Emby Server allows attackers to gain administrative server access without preconditions (critical 9.3)
- [CVE-2025-64325](https://insights.sbomify.com/CVE-2025-64325/): Emby Server is Vulnerable to Remote Code Execution Through XSS in Admin Dashboard (high 8.4)
- [CVE-2021-25828](https://insights.sbomify.com/CVE-2021-25828/): Cross-site scripting in n/a (medium 6.1)
- [CVE-2022-36223](https://insights.sbomify.com/CVE-2022-36223/): Cross-site scripting in n/a (medium 6.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-25827 and fix it if it is affected.

What it is: CVE-2021-25827 is a critical authentication bypass vulnerability in n/a, published on 28 Jun 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-25827 exists.

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-2021-25827/ (Markdown: https://insights.sbomify.com/CVE-2021-25827/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-25827
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-25827
- OSV: https://osv.dev/vulnerability/CVE-2021-25827

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-25827/
Summaries are generated and may contain mistakes; the official description above is the record.