CVE-2024-45614

Header normalization allows for client to clobber proxy set headers in Puma

Published Sep 19, 2024 CVSS 3.1 · 5.4 Medium EPSS < 1% KEV · Not listed
Description
Puma is a Ruby/Rack web server built for parallelism. In affected versions clients could clobber values set by intermediate proxies (such as X-Forwarded-For) by providing a underscore version of the same header (X-Forwarded_For). Any users relying on proxy set variables is affected. v6.4.3/v5.6.9 now discards any headers using underscores if the non-underscore version also exists. Effectively, allowing the proxy defined headers to always win. Users are advised to upgrade. Nginx has a underscores_in_headers configuration variable to discard these headers at the proxy level as a mitigation. Any users that are implicitly trusting the proxy defined headers for security should immediately cease doing so until upgraded to the fixed versions.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-3947-1 puma security update
EUVD EUVD EUVD-2024-2761 Puma is a Ruby/Rack web server built for parallelism. In affected versions clients could clobber values set by intermediate proxies (such as X-Forwarded-For) by providing a underscore version of the same header (X-Forwarded_For). Any users relying on proxy set variables is affected. v6.4.3/v5.6.9 now discards any headers using underscores if the non-underscore version also exists. Effectively, allowing the proxy defined headers to always win. Users are advised to upgrade. Nginx has a underscores_in_headers configuration variable to discard these headers at the proxy level as a mitigation. Any users that are implicitly trusting the proxy defined headers for security should immediately cease doing so until upgraded to the fixed versions.
Github GHSA Github GHSA GHSA-9hf4-67fc-4vf4 Puma's header normalization allows for client to clobber proxy set headers
Ubuntu USN Ubuntu USN USN-7031-1 Puma vulnerability
Ubuntu USN Ubuntu USN USN-7031-2 Puma vulnerability
History
Type Values Removed Values Added
Metrics epss

{'score': 0.00061}

epss

{'score': 0.00072}

Type Values Removed Values Added
First Time appeared Puma
Puma puma
Weaknesses CWE-444
CPEs cpe:2.3:a:puma:puma:*:*:*:*:*:ruby:*:*
Vendors & Products Puma
Puma puma
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description Puma is a Ruby/Rack web server built for parallelism. In affected versions clients could clobber values set by intermediate proxies (such as X-Forwarded-For) by providing a underscore version of the same header (X-Forwarded_For). Any users relying on proxy set variables is affected. v6.4.3/v5.6.9 now discards any headers using underscores if the non-underscore version also exists. Effectively, allowing the proxy defined headers to always win. Users are advised to upgrade. Nginx has a underscores_in_headers configuration variable to discard these headers at the proxy level as a mitigation. Any users that are implicitly trusting the proxy defined headers for security should immediately cease doing so until upgraded to the fixed versions.
Title Header normalization allows for client to clobber proxy set headers in Puma
Weaknesses CWE-639
References
Metrics cvssV3_1

{'score': 5.4, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Nov 3, 2025, 10:15 PM
Reserved
Sep 2, 2024, 4:00 PM
Status
Modified
Published
Sep 19, 2024, 11:15 PM
Modified
Jun 17, 2026, 7:54 AM
Severity
Moderate
Public date
Sep 19, 2024, 11:15 PM