# CVE-2021-27708: Command injection in n/a

> Remote attackers can execute arbitrary OS commands on TOTOLINK routers via modified HTTP requests due to unsafe system function usage.

- **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:** 14 Apr 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-x4fh-cj9q-q3x6

## What is CVE-2021-27708?

CVE-2021-27708 is a critical command injection vulnerability in Totolink X5000r Firmware, published on 14 Apr 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Command Injection in TOTOLINK X5000R router with firmware v9.1.0u.6118_B20201102, and TOTOLINK A720R router with firmware v4.1.5cu.470_B20200911 allows remote attackers to execute arbitrary OS commands by sending a modified HTTP request. This occurs because the function executes glibc's system function with untrusted input. In the function, "command" parameter is directly passed to the attacker, allowing them to control the "command" field to attack the OS.

Weakness: CWE-78 (Improper Neutralization of Special Elements used in an OS Command)

## Which versions are affected by CVE-2021-27708?

It affects 2 products.


Products: Totolink A720r Firmware, Totolink X5000r Firmware.

## How do I fix CVE-2021-27708?

No fix has been published for CVE-2021-27708 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-27708 being exploited?

There is no known exploitation of CVE-2021-27708 in the wild and no public exploit code.

## Other vulnerabilities in Totolink X5000r Firmware

- [CVE-2023-23064](https://insights.sbomify.com/CVE-2023-23064/): Missing authorization in n/a (critical 9.8)
- [CVE-2021-45740](https://insights.sbomify.com/CVE-2021-45740/): Denial of service in n/a (critical 9.8)
- [CVE-2021-45742](https://insights.sbomify.com/CVE-2021-45742/): Command injection in n/a (critical 9.8)
- [CVE-2021-35324](https://insights.sbomify.com/CVE-2021-35324/): Auth bypass in n/a (critical 9.8)
- [CVE-2021-35327](https://insights.sbomify.com/CVE-2021-35327/): Missing authorization in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-27708 and fix it if it is affected.

What it is: CVE-2021-27708 is a critical command injection vulnerability in Totolink X5000r Firmware, published on 14 Apr 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-2021-27708 in the wild and no public exploit code.

Affected product: Totolink X5000r 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-2021-27708/ (Markdown: https://insights.sbomify.com/CVE-2021-27708/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-27708
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-27708
- OSV: https://osv.dev/vulnerability/CVE-2021-27708

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-27708/
Summaries are generated and may contain mistakes; the official description above is the record.