CVE-2024-21647Network attack vector

Unauthenticated denial of service via unbounded chunk extensions

Published Jan 8, 2024 · Updated Nov 3, 2025

Denial of service in Puma before 5.6.8 and 6.0.0 through 6.4.1 allows remote attackers to exhaust CPU and bandwidth. Puma's HTTP/1.1 chunked-body parser accepts chunk-extension data without enforcing an upper size limit, allowing input processing to consume resources without bound. No authentication or user interaction is required; a crafted request can degrade or interrupt server availability.

CVSS severity5.9
Medium
EPSS probability0.96%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Puma before 5.6.8 and 6.0.0 through 6.4.1 allows remote attackers to exhaust CPU and bandwidth. Puma's HTTP/1.1 chunked-body parser accepts chunk-extension data without enforcing an upper size limit, allowing input processing to consume resources without bound. No authentication or user interaction is required; a crafted request can degrade or interrupt server availability.

The record

CVE
CVE-2024-21647
Published
Jan 8, 2024
Updated
Nov 3, 2025
Vendor
Puma
Product
Puma
Classifications
CWE-400, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 8, 2024CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 2025Record 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=< 5.6.8
  2. Affected versionversion=>= 6.0.0, < 6.4.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Puma · Pumaversion=< 5.6.8; version=>= 6.0.0, < 6.4.2

Published CVSS scores

5.9GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
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
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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