# CVE-2021-37136: Bzip2Decoder doesn't allow setting size restrictions for decompressed data

> Attackers can cause a denial of service via OutOfMemoryError in Netty's Bzip2 decoder by providing malicious input without size restrictions.

- **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-AS77854, CLEANSTART-2026-MT03413, CLSA-2025-1756771562, DEBIAN-CVE-2021-37136, GHSA-grg4-wf29-r9vv, MINI-364f-wpwc-r47v, MINI-5q59-5hmv-w53g, UBUNTU-CVE-2021-37136

## What is CVE-2021-37136?

CVE-2021-37136 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 Bzip2 decompression decoder function doesn't allow setting size restrictions on the decompressed output data (which affects the allocation size used during decompression). All users of Bzip2Decoder are affected. The malicious input can trigger an OOME and so a DoS attack

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2021-37136?

6 open source packages ship an affected version, including io.netty:netty, io.netty:netty-codec and org.jboss.netty:netty. It affects 19 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 | All versions | 4.1.68.Final |
| `io.netty:netty-codec` | Maven | All versions | 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 Coherence, Oracle Commerce Guided Search, Oracle Communications Brm - Elastic Charging Engine, Oracle Communications Cloud Native Core Binding Support Function, Oracle Communications Cloud Native Core Network Slice Selection Function, Oracle Communications Cloud Native Core Policy, Oracle Communications Cloud Native Core Security Edge Protection Proxy, Oracle Communications Cloud Native Core Unified Data Repository, Oracle Communications Diameter Signaling Router, Oracle Communications Instant Messaging Server, Oracle Helidon, Oracle Peoplesoft Enterprise Peopletools, Oracle Webcenter Portal, Quarkus Quarkus.

## How do I fix CVE-2021-37136?

Upgrade to a fixed version.

## Is CVE-2021-37136 being exploited?

There is no known exploitation of CVE-2021-37136 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-2021-37136 and fix it if it is affected.

What it is: CVE-2021-37136 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-2021-37136 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 all versions; fixed in 4.1.68.Final
- io.netty:netty-codec (Maven): affected all versions; 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-2021-37136/ (Markdown: https://insights.sbomify.com/CVE-2021-37136/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-37136
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-37136
- OSV: https://osv.dev/vulnerability/CVE-2021-37136

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-37136/
Summaries are generated and may contain mistakes; the official description above is the record.