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HIGH severity

CVE-2021-37136 — netty-codec

HIGHFix: netty/netty@41d3d61

CVE-2021-37136 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in io.netty:netty-codec. A fix is available for io.netty:netty-codec — see the affected versions and patch details below.

Bzip2Decoder doesn't allow setting size restrictions for decompressed data

Also known asGHSA-grg4-wf29-r9vv
Published
Updated
Affected
3 pkgs
Patched
1 / 3
Exploits
None indexed
Exploitation data as of Nov 11, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2021-37136.

EPSS Exploitation Probability

via FIRST.org ↗
5.9%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs93th percentile — riskier than 93% of all scored CVEsHighest risk
0.00%2.44%4.88%7.32%1.2%5.9%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

3 pkgs affected
☕io.netty:netty-codec☕org.jboss.netty:netty☕io.netty:netty

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Impact

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

Workarounds

No workarounds other than not using the Bzip2Decoder

References

Relevant code areas:

https://github.com/netty/netty/blob/netty-4.1.67.Final/codec/src/main/java/io/netty/handler/codec/compression/Bzip2Decoder.java#L80 https://github.com/netty/netty/blob/netty-4.1.67.Final/codec/src/main/java/io/netty/handler/codec/compression/Bzip2Decoder.java#L294 https://github.com/netty/netty/blob/netty-4.1.67.Final/codec/src/main/java/io/netty/handler/codec/compression/Bzip2Decoder.java#L305

Affected Packages

3 total 1 fixed
EcosystemPackageVulnerable rangeFix
☕Mavenio.netty:netty-codecall versions4.1.68.Finalio.netty:netty-codec:4.1.68.Final
☕Mavenorg.jboss.netty:nettyall versionsNo fix
☕Mavenio.netty:nettyall versionsNo fix

Affected Products

19 products · 38 configurations
OS
debian linuxdebian
2 versions
10.011.0
Application
oncommand insightnetapp
all
Application
nettynetty
< 4.1.68
range
Application
banking apisoracle
≥ 18.1 && ≤ 18.3
4 versions
19.119.220.121.1
Application
banking digital experienceoracle
7 versions
18.118.218.319.119.220.121.1
Application
coherenceoracle
2 versions
12.2.1.4.014.1.1.0.0

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.netty:netty-codec, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update io.netty:netty-codec to 4.1.68.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-37136 is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

In the OpenShift Container Platform (OCP), the Hive/Presto/Hadoop components that comprise the OCP Metering stack ship the vulnerable version of netty-codec package. Since the release of OCP 4.6, the Metering product has been deprecated [1], so the affected components are marked as wontfix. This may be fixed in the…

ProductFixed inAdvisory
Logging subsystem for Red Hat OpenShift 5.4openshift-logging/elasticsearch6-rhel8:v6.8.1-156RHSA-2022:2216
OpenShift Logging 5.1openshift-logging/elasticsearch6-rhel8:v6.8.1-67RHSA-2021:5128
OpenShift Logging 5.2openshift-logging/elasticsearch6-rhel8:v6.8.1-66RHSA-2021:5127
OpenShift Logging 5.2openshift-logging/elasticsearch6-rhel8:v6.8.1-157RHSA-2022:2218
OpenShift Logging 5.3openshift-logging/elasticsearch6-rhel8:v6.8.1-65RHSA-2021:5129
OpenShift Logging 5.3openshift-logging/elasticsearch6-rhel8:v6.8.1-159RHSA-2022:2217
Red Hat AMQ 7.9.1netty-codecRHSA-2021:4851
Red Hat AMQ Streams 2.0.0netty-codecRHSA-2022:0138
UbuntuHIGH
USN-6049-1Ubuntu

Frequently Asked Questions

### Impact 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 ### Workarounds No workarounds other than not using the `Bzip2Decoder` ### References Relevant code areas: https://github.com/netty/netty/blob/netty-4.1.67.Final/codec/src/main/java/io/netty/handler/codec/compression/Bzip2Decoder.java#L80 https://github.com/netty/netty/blob/netty-4.1.67.Final/codec/src/mai
O3 Security · Impact-Aware SCA

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CVE-2021-37136: netty-codec DoS — Fixed in 4.1.68.Final