# CVE-2021-20165: Cross-site request forgery in Trendnet AC2600 TEW-827DRU

> Attackers can bypass CSRF protections on Trendnet AC2600 routers to perform unauthorized actions on behalf of authenticated users.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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:** A user has to click or open something
- **Fix available:** No
- **Published:** 30 Dec 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-2fwv-796r-67vv

## What is CVE-2021-20165?

CVE-2021-20165 is a high-severity vulnerability in Trendnet AC2600 TEW-827DRU, published on 30 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

Trendnet AC2600 TEW-827DRU version 2.08B01 does not properly implement csrf protections. Most pages lack proper usage of CSRF protections or mitigations. Additionally, pages that do make use of CSRF tokens are trivially bypassable as the server does not appear to validate them properly (i.e. re-using an old token or finding the token thru some other method is possible).

Weakness: CWE-352 (Cross-Site Request Forgery)

## Which versions are affected by CVE-2021-20165?

It affects 1 product.


Products: Trendnet Tew-827dru Firmware.

## How do I fix CVE-2021-20165?

No fix has been published for CVE-2021-20165 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-20165 being exploited?

There is no known exploitation of CVE-2021-20165 in the wild and no public exploit code.

## Other vulnerabilities in Trendnet AC2600 TEW-827DRU

- [CVE-2024-28354](https://insights.sbomify.com/CVE-2024-28354/): Command injection in n/a (critical 10.0)
- [CVE-2021-20151](https://insights.sbomify.com/CVE-2021-20151/): Auth bypass in Trendnet AC2600 TEW-827DRU (critical 10.0)
- [CVE-2021-20149](https://insights.sbomify.com/CVE-2021-20149/): Missing authorization in Trendnet AC2600 TEW-827DRU (critical 9.8)
- [CVE-2021-20155](https://insights.sbomify.com/CVE-2021-20155/): Hardcoded credentials in Trendnet AC2600 TEW-827DRU (critical 9.8)
- [CVE-2021-20158](https://insights.sbomify.com/CVE-2021-20158/): Auth bypass in Trendnet AC2600 TEW-827DRU (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-20165 and fix it if it is affected.

What it is: CVE-2021-20165 is a high-severity vulnerability in Trendnet AC2600 TEW-827DRU, published on 30 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: There is no known exploitation of CVE-2021-20165 in the wild and no public exploit code.

Affected product: Trendnet AC2600 TEW-827DRU. 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-2021-20165/ (Markdown: https://insights.sbomify.com/CVE-2021-20165/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-20165
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-20165
- OSV: https://osv.dev/vulnerability/CVE-2021-20165

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-20165/
Summaries are generated and may contain mistakes; the official description above is the record.