CVE-2021-37137Network attack vector

Service interruption via unbounded Snappy chunk decoding

Published Oct 19, 2021 · Updated Aug 4, 2024

Uncontrolled resource consumption in Netty before 4.1.68.Final allows remote attackers to interrupt services via crafted Snappy data. SnappyFrameDecoder trusts declared chunk lengths, permits oversized decompressed output, and buffers entire reserved skippable chunks instead of discarding them incrementally. Exposure requires an application to pass attacker-controlled network streams or files through this decoder; memory exhaustion can terminate or stall that application.

CVSS severity7.5
High
EPSS probability6.74%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncontrolled resource consumption in Netty before 4.1.68.Final allows remote attackers to interrupt services via crafted Snappy data. SnappyFrameDecoder trusts declared chunk lengths, permits oversized decompressed output, and buffers entire reserved skippable chunks instead of discarding them incrementally. Exposure requires an application to pass attacker-controlled network streams or files through this decoder; memory exhaustion can terminate or stall that application.

The record

CVE
CVE-2021-37137
Published
Oct 19, 2021
Updated
Aug 4, 2024
Vendor
The Netty Project
Product
Netty
Classifications
CWE-400, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 19, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <4.1.68Final

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Netty Project · Nettyversion=unspecified <4.1.68Final

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.003Application Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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