# CVE-2020-27866: Auth bypass in Multiple Routers

> Network-adjacent attackers can bypass authentication on NETGEAR routers via flawed string matching in mini_httpd, potentially leading to root code execution.

- **Severity:** High 8.8 (`CVSS:3.0/AV:A/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:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 11 Feb 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-mj6p-ghhj-r3q4

## What is CVE-2020-27866?

CVE-2020-27866 is a high-severity authentication bypass vulnerability in Netgear R6020 Firmware, published on 11 Feb 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

This vulnerability allows network-adjacent attackers to bypass authentication on affected installations of NETGEAR R6020, R6080, R6120, R6220, R6260, R6700v2, R6800, R6900v2, R7450, JNR3210, WNR2020, Nighthawk AC2100, and Nighthawk AC2400 routers. Authentication is not required to exploit this vulnerability. The specific flaw exists within the mini_httpd service, which listens on TCP port 80 by default. The issue results from incorrect string matching logic when accessing protected pages. An attacker can leverage this in conjunction with other vulnerabilities to execute code in the context of root. Was ZDI-CAN-11355.

Weakness: CWE-287 (Improper Authentication), CWE-288 (Authentication Bypass Using an Alternate Path or Channel)

## Which versions are affected by CVE-2020-27866?

It affects 19 products.


Products: Netgear Ac2100 Firmware, Netgear Ac2400 Firmware, Netgear Ac2600 Firmware, Netgear R6020 Firmware, Netgear R6080 Firmware, Netgear R6120 Firmware, Netgear R6220 Firmware, Netgear R6230 Firmware, Netgear R6260 Firmware, Netgear R6330 Firmware, Netgear R6350 Firmware, Netgear R6700 Firmware, Netgear R6800 Firmware, Netgear R6850 Firmware, Netgear R6900 Firmware, Netgear R7200 Firmware, Netgear R7350 Firmware, Netgear R7400 Firmware, Netgear R7450 Firmware.

## How do I fix CVE-2020-27866?

No fix has been published for CVE-2020-27866 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-27866 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2020-27866 exists.

Public exploit code:

- NETGEAR - Authentication Bypass (nuclei): http/cves/2020/CVE-2020-27866.yaml

## Other vulnerabilities in Netgear R6020 Firmware

- [CVE-2021-38516](https://insights.sbomify.com/CVE-2021-38516/): Missing authorization in n/a (critical 10.0)
- [CVE-2021-29068](https://insights.sbomify.com/CVE-2021-29068/): Memory corruption in n/a (critical 9.9)
- [CVE-2020-35795](https://insights.sbomify.com/CVE-2020-35795/): Memory corruption in n/a (critical 9.8)
- [CVE-2020-35800](https://insights.sbomify.com/CVE-2020-35800/): Misconfiguration in n/a (critical 9.4)
- [CVE-2020-26927](https://insights.sbomify.com/CVE-2020-26927/): Auth bypass in n/a (critical 9.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-27866 and fix it if it is affected.

What it is: CVE-2020-27866 is a high-severity authentication bypass vulnerability in Netgear R6020 Firmware, published on 11 Feb 2021. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2020-27866 exists.

Affected product: Netgear R6020 Firmware. 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-2020-27866/ (Markdown: https://insights.sbomify.com/CVE-2020-27866/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-27866
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-27866
- OSV: https://osv.dev/vulnerability/CVE-2020-27866

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-27866/
Summaries are generated and may contain mistakes; the official description above is the record.