VYPR
← All advisories
Moderate severityNVD Advisory· Published Sep 19, 2024· Updated Nov 3, 2025

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

CVE-2024-45614

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.

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
pumaRubyGems
< 5.6.95.6.9
pumaRubyGems
>= 6.0.0, < 6.4.36.4.3

Affected products

127

Patches

Vulnerability mechanics

References

8

News mentions

0

No linked articles in our index yet.