PT-2026-47626 · Rubygems · Puma

Published

2026-06-09

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Updated

2026-06-09

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CVE-2026-47737

CVSS v3.1

7.5

High

VectorAV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Impact

Puma is vulnerable to source IP spoofing when set remote address proxy protocol: :v1 is enabled and persistent connections are used.
PROXY protocol v1 is a connection-level protocol. Support was added to Puma in v5.5.0. A proxy sends one PROXY header at the beginning of a TCP connection, before any HTTP data. Puma incorrectly re-parsed PROXY protocol headers after each keep-alive request on the same connection. An attacker able to send HTTP requests through a trusted proxy could therefore inject a second PROXY header between HTTP requests. Puma would treat the injected header as authoritative for the next request and overwrite REMOTE ADDR.
This can mislead applications or middleware that use REMOTE ADDR for security decisions, rate limiting, auditing, or allow/deny lists.
Only deployments that explicitly enable PROXY protocol v1 are affected, and will have set:
set remote address proxy protocol: :v1
Puma's default configuration is not affected. Deployments that do not use persistent connections to Puma are also not expected to be affected by this issue.

Patches

Users should upgrade to versions 7.2.1 or 8.0.2.

Workarounds

Disable PROXY protocol v1 parsing if it is not required:
 # remove/comment this:
 # set remote address proxy protocol: :v1
Users can also disable persistent connections to Puma, for example:
enable keep alives false

References

Exploit

Fix

Insufficient Verification of Data Authenticity

Authentication Bypass by Spoofing

Weakness Enumeration

CWE-345CWE-290

Related Identifiers

CVE-2026-47737
GHSA-2VQW-3MP8-CGMX

Affected Products

Puma