# CVE-2021-4000: Open Redirect in star7th/showdoc

> Attackers can redirect users to malicious sites via ShowDoc, potentially facilitating phishing attacks against documentation users.

- **Severity:** Medium 6.5 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/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:** 3 Dec 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-8c9x-wfgj-v78w

## What is CVE-2021-4000?

CVE-2021-4000 is a medium-severity vulnerability in star7th/showdoc, published on 3 Dec 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

showdoc is vulnerable to URL Redirection to Untrusted Site

Weakness: CWE-601 (URL Redirection to Untrusted Site)

## Which versions are affected by CVE-2021-4000?

2 open source packages ship an affected version, including showdoc/showdoc. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `showdoc/showdoc` | Packagist | All versions to 2.9.13 | None |
| `showdoc/showdoc` | Packagist | All versions to 2.9.13 | None |

Products: Showdoc Showdoc.

## How do I fix CVE-2021-4000?

No fix has been published for CVE-2021-4000 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-4000 being exploited?

There is no known exploitation of CVE-2021-4000 in the wild and no public exploit code.

## Other vulnerabilities in star7th/showdoc

- [CVE-2021-41745](https://insights.sbomify.com/CVE-2021-41745/): Showdoc File Upload Vulnerability (critical 9.8)
- [CVE-2021-36440](https://insights.sbomify.com/CVE-2021-36440/): Unrestricted File Upload in ShowDoc v2.9.5 (critical 9.8)
- [CVE-2022-0942](https://insights.sbomify.com/CVE-2022-0942/): Stored XSS due to Unrestricted File Upload in star7th/showdoc (critical 9.4)
- [CVE-2022-1034](https://insights.sbomify.com/CVE-2022-1034/): There is a Unrestricted Upload of File vulnerability in ShowDoc v2.10.3 in star7th/showdoc (critical 9.1)
- [CVE-2022-0945](https://insights.sbomify.com/CVE-2022-0945/): Stored XSS viva axd and cshtml file upload in star7th/showdoc in star7th/showdoc (critical 9.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-4000 and fix it if it is affected.

What it is: CVE-2021-4000 is a medium-severity vulnerability in star7th/showdoc, published on 3 Dec 2021. 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-2021-4000 in the wild and no public exploit code.

Affected packages and fixed versions:
- showdoc/showdoc (Packagist): affected all versions up to 2.9.13; no fix listed
- showdoc/showdoc (Packagist): affected all versions up to 2.9.13; no fix listed

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-2021-4000/ (Markdown: https://insights.sbomify.com/CVE-2021-4000/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-4000
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-4000
- OSV: https://osv.dev/vulnerability/CVE-2021-4000

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-4000/
Summaries are generated and may contain mistakes; the official description above is the record.