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.
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No Fix Known
No patch has been released yet. Apply workarounds or mitigations where available.
Published
CVE disclosed publicly
Last Modified
Most recent update
Indexed to CVEInsight
Added to this platform
AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
2
Affected Products
3
References
puma / puma
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
Exploitability
Impact