# CVE-2021-20137: Cross-site scripting in Gryphon Tower router

> Reflected XSS in Gryphon Tower router allows attackers to execute JavaScript in victim browsers via crafted links.

- **Severity:** Medium 6.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 9 Dec 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-3m6f-2h66-fxv5

## What is CVE-2021-20137?

CVE-2021-20137 is a medium-severity cross-site scripting vulnerability in Gryphon Tower router, published on 9 Dec 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

A reflected cross-site scripting vulnerability exists in the url parameter of the /cgi-bin/luci/site_access/ page on the Gryphon Tower router's web interface. An attacker could exploit this issue by tricking a user into following a specially crafted link, granting the attacker javascript execution in the context of the victim's browser.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2021-20137?

It affects 1 product.


Products: Gryphonconnect Gryphon Tower Firmware.

## How do I fix CVE-2021-20137?

No fix has been published for CVE-2021-20137 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-20137 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-20137 exists.

Public exploit code:

- Gryphon Tower - Cross-Site Scripting (nuclei): http/cves/2021/CVE-2021-20137.yaml

## Other vulnerabilities in Gryphon Tower router

- [CVE-2021-20146](https://insights.sbomify.com/CVE-2021-20146/): Hardcoded credentials in Gryphon Tower router (critical 9.8)
- [CVE-2021-20138](https://insights.sbomify.com/CVE-2021-20138/): Command injection in Gryphon Tower router (high 8.8)
- [CVE-2021-20139](https://insights.sbomify.com/CVE-2021-20139/): Command injection in Gryphon Tower router (high 8.8)
- [CVE-2021-20140](https://insights.sbomify.com/CVE-2021-20140/): Command injection in Gryphon Tower router (high 8.8)
- [CVE-2021-20141](https://insights.sbomify.com/CVE-2021-20141/): Command injection in Gryphon Tower router (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-20137 and fix it if it is affected.

What it is: CVE-2021-20137 is a medium-severity cross-site scripting vulnerability in Gryphon Tower router, published on 9 Dec 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-20137 exists.

Affected product: Gryphon Tower router. 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-2021-20137/ (Markdown: https://insights.sbomify.com/CVE-2021-20137/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-20137
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-20137
- OSV: https://osv.dev/vulnerability/CVE-2021-20137

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-20137/
Summaries are generated and may contain mistakes; the official description above is the record.