# CVE-2021-37137: SnappyFrameDecoder doesn't restrict chunk length any may buffer skippable chunks in an unnecessary way

> Attackers can cause excessive memory usage and denial of service in Netty applications by sending malicious compressed data or large skippable chunks.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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:** 19 Oct 2021
- **Updated:** 8 Oct 2026
- **Also known as:** CLEANSTART-2026-FK73993, DEBIAN-CVE-2021-37137, GHSA-9vjp-v76f-g363, MINI-m5mh-mmvq-grg4, MINI-rm58-h3jr-4vvc, UBUNTU-CVE-2021-37137

## What is CVE-2021-37137?

CVE-2021-37137 is a high-severity denial of service vulnerability in Debian Debian Linux, published on 19 Oct 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The Snappy frame decoder function doesn't restrict the chunk length which may lead to excessive memory usage. Beside this it also may buffer reserved skippable chunks until the whole chunk was received which may lead to excessive memory usage as well. This vulnerability can be triggered by supplying malicious input that decompresses to a very big size (via a network stream or a file) or by sending a huge skippable chunk.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2021-37137?

6 open source packages ship an affected version, including io.netty:netty, io.netty:netty-codec and org.jboss.netty:netty. It affects 12 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `io.netty:netty` | Maven | All versions | None |
| `io.netty:netty` | Maven | All versions | None |
| `io.netty:netty-codec` | Maven | From 4.0.0 | 4.1.68.Final |
| `io.netty:netty-codec` | Maven | From 4.0.0 | 4.1.68.Final |
| `org.jboss.netty:netty` | Maven | All versions | None |
| `org.jboss.netty:netty` | Maven | All versions | None |

Products: Debian Debian Linux, Netapp Oncommand Insight, Netty Netty, Oracle Banking Apis, Oracle Banking Digital Experience, Oracle Commerce Guided Search, Oracle Communications Brm - Elastic Charging Engine, Oracle Communications Cloud Native Core Binding Support Function, Oracle Communications Diameter Signaling Router, Oracle Peoplesoft Enterprise Peopletools, Oracle Webcenter Portal, Quarkus Quarkus.

## How do I fix CVE-2021-37137?

Upgrade to a fixed version.

## Is CVE-2021-37137 being exploited?

There is no known exploitation of CVE-2021-37137 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-37137 and fix it if it is affected.

What it is: CVE-2021-37137 is a high-severity denial of service vulnerability in Debian Debian Linux, published on 19 Oct 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-2021-37137 in the wild and no public exploit code.

Affected packages and fixed versions:
- io.netty:netty (Maven): affected all versions; no fix listed
- io.netty:netty (Maven): affected all versions; no fix listed
- io.netty:netty-codec (Maven): affected from 4.0.0; fixed in 4.1.68.Final
- io.netty:netty-codec (Maven): affected from 4.0.0; fixed in 4.1.68.Final
- org.jboss.netty:netty (Maven): affected all versions; no fix listed
- org.jboss.netty:netty (Maven): affected all versions; no fix listed

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-2021-37137/ (Markdown: https://insights.sbomify.com/CVE-2021-37137/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-37137
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-37137
- OSV: https://osv.dev/vulnerability/CVE-2021-37137

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-37137/
Summaries are generated and may contain mistakes; the official description above is the record.