# CVE-2021-42387: Memory corruption in clickhouse

> An attacker can trigger a heap out-of-bounds read in ClickHouse via a malicious query, potentially causing a crash or leaking memory.

- **Severity:** High 8.1 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/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:** 14 Mar 2022
- **Updated:** 4 Aug 2024
- **Also known as:** DEBIAN-CVE-2021-42387, GHSA-cf9g-639p-3wvv, UBUNTU-CVE-2021-42387

## What is CVE-2021-42387?

CVE-2021-42387 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 14 Mar 2022. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Heap out-of-bounds read in Clickhouse's LZ4 compression codec when parsing a malicious query. As part of the LZ4::decompressImpl() loop, a 16-bit unsigned user-supplied value ('offset') is read from the compressed data. The offset is later used in the length of a copy operation, without checking the upper bounds of the source of the copy operation.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2021-42387?

It affects 2 products.


Products: Clickhouse Clickhouse, Debian Debian Linux.

## How do I fix CVE-2021-42387?

Upgrade to a fixed version.

## Is CVE-2021-42387 being exploited?

There is no known exploitation of CVE-2021-42387 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2019-16535](https://insights.sbomify.com/CVE-2019-16535/): Memory corruption in ClickHouse (critical 9.8)
- [CVE-2018-14670](https://insights.sbomify.com/CVE-2018-14670/): Missing authorization in ClickHouse (critical 9.8)
- [CVE-2018-14671](https://insights.sbomify.com/CVE-2018-14671/): Code injection in ClickHouse (critical 9.8)
- [CVE-2021-43304](https://insights.sbomify.com/CVE-2021-43304/): Memory corruption in clickhouse (high 8.8)
- [CVE-2021-43305](https://insights.sbomify.com/CVE-2021-43305/): Memory corruption in clickhouse (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-42387 and fix it if it is affected.

What it is: CVE-2021-42387 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 14 Mar 2022. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-42387 in the wild and no public exploit code.

Affected product: Debian Debian Linux. 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-2021-42387/ (Markdown: https://insights.sbomify.com/CVE-2021-42387/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-42387
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-42387
- OSV: https://osv.dev/vulnerability/CVE-2021-42387

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-42387/
Summaries are generated and may contain mistakes; the official description above is the record.