# CVE-2021-31522: Apache Kylin unsafe class loading

> Attacker can execute arbitrary code via unsafe class loading in Apache Kylin, requiring immediate upgrade to patched versions.

- **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:** 6 Jan 2022
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-q656-g2x3-8cgh

## What is CVE-2021-31522?

CVE-2021-31522 is a critical code injection vulnerability in Apache Kylin, published on 6 Jan 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Kylin can receive user input and load any class through Class.forName(...). This issue affects Apache Kylin 2 version 2.6.6 and prior versions; Apache Kylin 3 version 3.1.2 and prior versions; Apache Kylin 4 version 4.0.0 and prior versions.

Weakness: CWE-470 (Use of Externally-Controlled Input to Select Classes or Code)

## Which versions are affected by CVE-2021-31522?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `org.apache.kylin:kylin` | Maven | All versions | 3.1.3 |
| `org.apache.kylin:kylin` | Maven | All versions | 3.1.3 |
| `org.apache.kylin:kylin` | Maven | From 4.0.0 | 4.0.1 |
| `org.apache.kylin:kylin` | Maven | From 4.0.0 | 4.0.1 |

Products: Apache Kylin.

## How do I fix CVE-2021-31522?

Upgrade org.apache.kylin:kylin to a fixed version for your release line: 3.1.3 or 4.0.1.

## Is CVE-2021-31522 being exploited?

There is no known exploitation of CVE-2021-31522 in the wild and no public exploit code.

## Other vulnerabilities in Apache Kylin

- [CVE-2020-1956](https://insights.sbomify.com/CVE-2020-1956/): Apache Kylin OS Command Injection (high 8.8, exploited in the wild)
- [CVE-2026-62390](https://insights.sbomify.com/CVE-2026-62390/): Apache Kylin: SQL Injection Vulnerability in Catalog Cache Refresh API (critical 9.8)
- [CVE-2022-44621](https://insights.sbomify.com/CVE-2022-44621/): Apache Kylin: Command injection by Diagnosis Controller (critical 9.8)
- [CVE-2022-24697](https://insights.sbomify.com/CVE-2022-24697/): Apache Kylin vulnerable to remote code execution (critical 9.8)
- [CVE-2021-45456](https://insights.sbomify.com/CVE-2021-45456/): Command injection (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-31522 and fix it if it is affected.

What it is: CVE-2021-31522 is a critical code injection vulnerability in Apache Kylin, published on 6 Jan 2022. 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-2021-31522 in the wild and no public exploit code.

Affected packages and fixed versions:
- org.apache.kylin:kylin (Maven): affected all versions; fixed in 3.1.3
- org.apache.kylin:kylin (Maven): affected all versions; fixed in 3.1.3
- org.apache.kylin:kylin (Maven): affected from 4.0.0; fixed in 4.0.1
- org.apache.kylin:kylin (Maven): affected from 4.0.0; fixed in 4.0.1

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-2021-31522/ (Markdown: https://insights.sbomify.com/CVE-2021-31522/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-31522
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-31522
- OSV: https://osv.dev/vulnerability/CVE-2021-31522

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-31522/
Summaries are generated and may contain mistakes; the official description above is the record.