CVE-2024-21647: Puma Puma HTTP Request/Response Smuggling Vulnerability Vulnerability

MODERATE
Advisory Identifier: GHSA-c2f4-cvqm-65w2
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CVSS 5.9
CWE-444
Published
Advisory Summary

CVE-2024-21647 is a MODERATE (CVSS 5.9) puma http request/response smuggling vulnerability vulnerability (CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')) affecting Puma libraries in the RubyGems ecosystem. The issue involves puma http request/response smuggling vulnerability. Remediation is available by upgrading affected packages to version 6.4.2, 5.6.8.

CVE-2024-21647 at a Glance

CVE Identifier CVE-2024-21647
GHSA Identifier GHSA-c2f4-cvqm-65w2
Severity MODERATE
CVSS v3.1 Base Score 5.9
CWE Classification CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Affected Product Puma
Package Ecosystem RubyGems
Published Date
Last Updated

Security Impact

CVSS: 5.9

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2024-21647

To remediate this vulnerability, upgrade all affected Puma dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

puma fixed: 6.4.2 
Upgrade puma to 6.4.2
puma fixed: 5.6.8 
Upgrade puma to 5.6.8
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for puma

How to Check if You Are Affected

To determine whether your application is affected by CVE-2024-21647, inspect your project dependencies for Puma:

inspect dependencies for puma

Analyze the terminal output to locate any version of Puma in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 6.4.2), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling'), where the product acts as an intermediary http agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed http requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination. In Puma, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact Prior to versions 6.4.2 and 5.6.8, puma exhibited dangerous behavior when parsing chunked transfer encoding bodies. Fixed versions limit the size of chunk extensions. Without this limit, an attacker could cause unbounded resource (CPU, network bandwidth) consumption. ### Patches The vulnerability has been fixed in 6.4.2 and 5.6.8. ### Workarounds No known workarounds. ### References * [HTTP Request Smuggling](https://portswigger.net/web-security/request-smuggling) * Open an issue in [Puma](https://github.com/puma/puma) * See our [security policy](https://github.com/puma/puma/security/policy)

CVE-2024-21647 Affected Puma Versions

2 component(s)
Fixed Versions:
6.4.25.6.8
Product / Package Ecosystem Affected Versions Fixed Version
puma
gem/puma
RubyGems
≥ 6.0.0
< 6.4.2
6.4.2
puma
gem/puma
RubyGems
< 5.6.8
5.6.8

References

GitHub Advisory / Wiki ADVISORY
https://github.com/puma/puma/security/advisories/GHSA-c2f4-cvqm-65w2
NVD — CVE-2024-21647 NVD
https://nvd.nist.gov/vuln/detail/CVE-2024-21647
Security Fix Commit FIX COMMIT
https://github.com/puma/puma/commit/5fc43d73b6ff193325e657a24ed76dec79133e93
Security Fix Commit FIX COMMIT
https://github.com/puma/puma/commit/60d5ee3734adc8cee85c3f0561af392448fe19b7
Security Fix Commit FIX COMMIT
https://github.com/puma/puma/commit/bbb880ffb6debbfdea535b4b3eb2204d49ae151d
Puma Source Repository REPOSITORY
https://github.com/puma/puma
Puma Source Repository REPOSITORY
https://github.com/rubysec/ruby-advisory-db/blob/master/gems/puma/CVE-2024-21647.yml
lists.debian.org/debian-lts-announce... WEB
https://lists.debian.org/debian-lts-announce/2024/11/msg00004.html

Frequently Asked Questions

What is CVE-2024-21647?
CVE-2024-21647 is a security vulnerability in Puma involving Puma HTTP Request/Response Smuggling vulnerability under CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling').
Which Puma versions are affected?
Affected versions include releases prior to 6.4.2, 5.6.8 across affected packages: puma.
What version fixes CVE-2024-21647?
Upgrading to 6.4.2, 5.6.8 (or the latest patched release for your respective branch) resolves the vulnerability.
Is puma affected?
Yes, puma is affected in releases prior to 6.4.2, 5.6.8. Upgrade your dependency to 6.4.2, 5.6.8 or later.
What is the CVSS score of CVE-2024-21647?
CVE-2024-21647 has a CVSS v3.1 base score of 5.9 (MODERATE) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2024-21647?
CVE-2024-21647 is classified under CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') (The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.).
How can I check RubyGems dependencies for CVE-2024-21647?
Run the dependency tree command: 'inspect dependencies for puma'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-c2f4-cvqm-65w2",
  "modified" : "2025-11-04T16:49:07Z",
  "published" : "2024-01-08T15:56:48Z",
  "aliases" : [ "CVE-2024-21647" ],
  "summary" : "Puma HTTP Request/Response Smuggling vulnerability",
  "details" : "### Impact\nPrior to versions 6.4.2 and 5.6.8, puma exhibited dangerous behavior when parsing chunked transfer encoding bodies.\n\nFixed versions limit the size of chunk extensions. Without this limit, an attacker could cause unbounded resource (CPU, network bandwidth) consumption.\n\n### Patches\n\nThe vulnerability has been fixed in 6.4.2 and 5.6.8.\n\n### Workarounds\n\nNo known workarounds.\n\n### References\n\n* [HTTP Request Smuggling](https://portswigger.net/web-security/request-smuggling)\n* Open an issue in [Puma](https://github.com/puma/puma)\n* See our [security policy](https://github.com/puma/puma/security/policy)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "puma"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "6.0.0"
      }, {
        "fixed" : "6.4.2"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "puma"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "5.6.8"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/puma/puma/security/advisories/GHSA-c2f4-cvqm-65w2"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2024-21647"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/puma/puma/commit/5fc43d73b6ff193325e657a24ed76dec79133e93"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/puma/puma/commit/60d5ee3734adc8cee85c3f0561af392448fe19b7"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/puma/puma/commit/bbb880ffb6debbfdea535b4b3eb2204d49ae151d"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/puma/puma"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rubysec/ruby-advisory-db/blob/master/gems/puma/CVE-2024-21647.yml"
  }, {
    "type" : "WEB",
    "url" : "https://lists.debian.org/debian-lts-announce/2024/11/msg00004.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-444" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2024-01-08T15:56:48Z",
    "nvd_published_at" : "2024-01-08T14:15:47Z"
  }
}