CVE-2024-21647: HTTP Request/Response Smuggling in puma
Vulnerability summary
CVE-2024-21647 is a high (CVSS 7.5) vulnerability in puma. EPSS estimates a 0.96% chance of exploitation in the next 30 days, higher than 61.5% of scored vulnerabilities.
Not severe (CVSS 5.9, network access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 6 · Related 7Timeline
- 08-01-2024PublishedVulnerability first disclosed.
- 03-11-2025Last modifiedVulnerability information updated.
Description
Puma is a web server for Ruby/Rack applications built for parallelism. Prior to version 6.4.2, puma exhibited incorrect behavior when parsing chunked transfer encoding bodies in a way that allowed HTTP request smuggling. Fixed versions limits the size of chunk extensions. Without this limit, an attacker could cause unbounded resource (CPU, network bandwidth) consumption. This vulnerability has been fixed in versions 6.4.2 and 5.6.8.
CVSS metrics
7 scores · 7 sources · 1 version- CVE.orgCNA5.9MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:HDiffers
- OSV · UbuntuEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · WolfiEcosystem advisory · calculated5.9MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:HDiffers
- OSV · ChainguardEcosystem advisory · calculated5.9MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:HDiffers
- OSV · RubygemsEcosystem advisory · calculated5.9MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:HDiffers
EPSS trend
Probability
0.96%
Chance of exploitation in the next 30 days
Percentile
62%
Versus all other CVEs
30-day change
No change 0.00 pp
From 0.96% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Chainguard1 product
- ruby3.2-puma< 6.4.2-r0
Debian1 product
- puma< 5.6.5-3+deb12u1 | < 6.4.2-1
Puma1 product
- puma< 5.6.8 | ≥ 6.0.0, < 6.4.2
RubyGems1 product
- puma≥ 6.0.0, < 6.4.2 | < 5.6.8
Ubuntu1 product
- puma< 3.12.4-1ubuntu2+esm1 | < 5.5.2-2ubuntu2+esm1
Wolfi1 product
- ruby3.2-puma< 6.4.2-r0
6 vendors · 6 products
References
14 links- github.com/puma/puma/security/advisories/GHSA-c2f4-cvqm-65w2X Refsource CONFIRMREPORTAdvisoryWEBVendor Advisory
