# CVE-2021-36162: Unprotected yaml deserialization cause RCE

> An attacker with configuration center access can poison YAML rules to achieve remote code execution on Dubbo consumers via unsafe SnakeYAML deserialization.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 7 Sep 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-r577-4hq7-73qh

## What is CVE-2021-36162?

CVE-2021-36162 is a high-severity unsafe deserialization vulnerability in Apache Dubbo, published on 7 Sep 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Apache Dubbo supports various rules to support configuration override or traffic routing (called routing in Dubbo). These rules are loaded into the configuration center (eg: Zookeeper, Nacos, ...) and retrieved by the customers when making a request in order to find the right endpoint. When parsing these YAML rules, Dubbo customers will use SnakeYAML library to load the rules which by default will enable calling arbitrary constructors. An attacker with access to the configuration center he will be able to poison the rule so when retrieved by the consumers, it will get RCE on all of them. This was fixed in Dubbo 2.7.13, 3.0.2

## Which versions are affected by CVE-2021-36162?

4 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 |
| `org.apache.dubbo:dubbo` | Maven | From 3.0.0 | 3.0.2 |
| `org.apache.dubbo:dubbo` | Maven | From 3.0.0 | 3.0.2 |

Products: Apache Dubbo.

## How do I fix CVE-2021-36162?

Upgrade org.apache.dubbo:dubbo to a fixed version for your release line: 2.7.13 or 3.0.2.

## Is CVE-2021-36162 being exploited?

There is no known exploitation of CVE-2021-36162 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-2021-36162 and fix it if it is affected.

What it is: CVE-2021-36162 is a high-severity unsafe deserialization vulnerability in Apache Dubbo, published on 7 Sep 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-36162 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
- org.apache.dubbo:dubbo (Maven): affected from 3.0.0; fixed in 3.0.2
- org.apache.dubbo:dubbo (Maven): affected from 3.0.0; fixed in 3.0.2

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-2021-36162/ (Markdown: https://insights.sbomify.com/CVE-2021-36162/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-36162
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-36162
- OSV: https://osv.dev/vulnerability/CVE-2021-36162

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-36162/
Summaries are generated and may contain mistakes; the official description above is the record.