How severe is CVE-2021-37137?

CVE-2021-37137 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-37137?

CVE-2021-37137 affects the following packages: io.netty:netty-codec (Maven), org.jboss.netty:netty (Maven), io.netty:netty (Maven). Ecosystems affected: Maven.

How do I fix CVE-2021-37137?

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-2021-37137 is resolved across your whole dependency graph.

How do I detect CVE-2021-37137 in my Maven dependencies?

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.

How do I mitigate CVE-2021-37137 if there is no patch (or I can't update yet)?

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.

Is CVE-2021-37137 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-37137 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2021-37137?

CVE-2021-37137 has an EPSS (Exploit Prediction Scoring System) score of 6.6%, placing it in the 94th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2021-37137?

CVE-2021-37137 is classified as Uncontrolled Resource Consumption (CWE-400). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2021-37137 published, and has it been updated?

CVE-2021-37137 was published on October 19, 2021 and was last updated on October 24, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕

☕ Maven

Not in CISA KEV

HIGH severity

CVE-2021-37137 — netty-codec

HIGHFix: netty/netty@6da4956

CVE-2021-37137 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.

SnappyFrameDecoder doesn't restrict chunk length any may buffer skippable chunks in an unnecessary way

Also known asGHSA-9vjp-v76f-g363

Published

Oct 19, 2021

Updated

Oct 24, 2026

Affected

3 pkgs

Patched

1 / 3

Exploits

None indexed

Exploitation data as of Nov 10, 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-2021-37137.

EPSS Exploitation Probability

via FIRST.org ↗

6.6%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs94th percentile — riskier than 94% of all scored CVEsHighest risk

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 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.

Impact

All users of SnappyFrameDecoder are affected and so the application may be in risk for a DoS attach due excessive memory usage.

References

https://github.com/netty/netty/blob/netty-4.1.67.Final/codec/src/main/java/io/netty/handler/codec/compression/SnappyFrameDecoder.java#L79 https://github.com/netty/netty/blob/netty-4.1.67.Final/codec/src/main/java/io/netty/handler/codec/compression/SnappyFrameDecoder.java#L171 https://github.com/netty/netty/blob/netty-4.1.67.Final/codec/src/main/java/io/netty/handler/codec/compression/SnappyFrameDecoder.java#L185

Affected Packages

3 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`io.netty:netty-codec`	≥ 4.0.0&&< 4.1.68.Final	4.1.68.Final`io.netty:netty-codec:4.1.68.Final`
☕Maven	`org.jboss.netty:netty`	all versions	No fix
☕Maven	`io.netty:netty`	all versions	No fix

Affected Products

12 products · 27 configurations

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

commerce guided searchoracle

1 version

11.3.2

Detection & mitigation playbook

Open-source dependency

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.
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-2021-37137 is resolved across your whole dependency graph.
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 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], hence the affected components are marked as wontfix. This may be fixed in the…

Product	Fixed in	Advisory
Logging subsystem for Red Hat OpenShift 5.4	`openshift-logging/elasticsearch6-rhel8:v6.8.1-156`	RHSA-2022:2216
OpenShift Logging 5.1	`openshift-logging/elasticsearch6-rhel8:v6.8.1-67`	RHSA-2021:5128
OpenShift Logging 5.2	`openshift-logging/elasticsearch6-rhel8:v6.8.1-66`	RHSA-2021:5127
OpenShift Logging 5.2	`openshift-logging/elasticsearch6-rhel8:v6.8.1-157`	RHSA-2022:2218
OpenShift Logging 5.3	`openshift-logging/elasticsearch6-rhel8:v6.8.1-65`	RHSA-2021:5129
OpenShift Logging 5.3	`openshift-logging/elasticsearch6-rhel8:v6.8.1-159`	RHSA-2022:2217
Red Hat AMQ 7.9.1	`netty-codec`	RHSA-2021:4851
Red Hat AMQ Streams 2.0.0	`netty-codec`	RHSA-2022:0138

UbuntuHIGH

USN-6049-1Ubuntu

Frequently Asked Questions

### Impact 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. ### Impact All users of SnappyFrameDecoder are affected and so the application may be in risk for a DoS attach due excessive memory usage. ### References https:

O3 Security · Impact-Aware SCA

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CVE-2021-37137 — netty-codec

Exploitation Status

No confirmed exploitation observed yet

EPSS Exploitation Probability

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

Description

Impact

Impact

References

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Fixing This On Your OS

Frequently Asked Questions

Is CVE-2021-37137 in your dependencies?