# CVE-2021-36161: Unprotected input value toString cause RCE

> Attackers can achieve remote code execution by providing malicious input that triggers unsafe toString methods in Apache Dubbo components.

- **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:** Yes
- **Published:** 9 Sep 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-qvm7-23cj-437v

## What is CVE-2021-36161?

CVE-2021-36161 is a critical code injection vulnerability in Apache Dubbo, published on 9 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Some component in Dubbo will try to print the formated string of the input arguments, which will possibly cause RCE for a maliciously customized bean with special toString method. In the latest version, we fix the toString call in timeout, cache and some other places. Fixed in Apache Dubbo 2.7.13

Weakness: CWE-134 (Use of Externally-Controlled Format String)

## Which versions are affected by CVE-2021-36161?

2 open source packages ship an affected version, including org.apache.dubbo:dubbo. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `org.apache.dubbo:dubbo` | Maven | All versions | 2.7.13 |
| `org.apache.dubbo:dubbo` | Maven | All versions | 2.7.13 |

Products: Apache Dubbo.

## How do I fix CVE-2021-36161?

Upgrade org.apache.dubbo:dubbo to 2.7.13 or later.

## Is CVE-2021-36161 being exploited?

There is no known exploitation of CVE-2021-36161 in the wild and no public exploit code.

## Other vulnerabilities in Apache Dubbo

- [CVE-2023-29234](https://insights.sbomify.com/CVE-2023-29234/): Bypass serialize checks in Apache Dubbo (critical 9.8)
- [CVE-2023-46279](https://insights.sbomify.com/CVE-2023-46279/): Apache Dubbo: Bypass deny serialize list check in Apache Dubbo (critical 9.8)
- [CVE-2021-32824](https://insights.sbomify.com/CVE-2021-32824/): Regular expression Denial of Service in MooTools (critical 9.8)
- [CVE-2022-39198](https://insights.sbomify.com/CVE-2022-39198/): Apache Dubbo Hession Deserialization Vulnerability Gadgets Bypass (critical 9.8)
- [CVE-2021-43297](https://insights.sbomify.com/CVE-2021-43297/): Dubbo Hessian cause RCE when parse error (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-36161 and fix it if it is affected.

What it is: CVE-2021-36161 is a critical code injection vulnerability in Apache Dubbo, published on 9 Sep 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-2021-36161 in the wild and no public exploit code.

Affected packages and fixed versions:
- org.apache.dubbo:dubbo (Maven): affected all versions; fixed in 2.7.13
- org.apache.dubbo:dubbo (Maven): affected all versions; fixed in 2.7.13

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-2021-36161/ (Markdown: https://insights.sbomify.com/CVE-2021-36161/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-36161
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-36161
- OSV: https://osv.dev/vulnerability/CVE-2021-36161

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-36161/
Summaries are generated and may contain mistakes; the official description above is the record.