Live › vulnerability › CVE-2026-47737
Puma accepted a second PROXY protocol v1 header sent on a persistent connection and overwrote REMOTE_ADDR with it. An attacker who can send requests through a trusted proxy can make applications see a forged client IP for security checks, rate limits, audit logs and allow/deny lists.
Summary written from the sources below. Check the originals before acting.
First seen by InfraStack 2026-11-02 22:13 UTC, 0h before NVD. All times on this page are UTC.
Only Ruby applications served by Puma that explicitly enable set_remote_address proxy_protocol: :v1 and accept persistent connections through a proxy are exposed. The default Puma configuration is not affected, and deployments without persistent connections are not expected to be affected.
| Product | Ecosystem | Affected | Fixed in |
|---|---|---|---|
| puma | rubygems | >= 8.0.0, < 8.0.2 | 8.0.2 |
| puma | rubygems | >= 5.5.0, < 7.2.1 | 7.2.1 |
Unknown from the sources.
8.0.2 for the 8.0 line7.2.1 for the 7.x lineset_remote_address proxy_protocol: :v1 if PROXY protocol v1 is not required, or set enable_keep_alives false.Each row is the first time that source carried this signal. The analyst’s rows are its own findings.
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.
Users should upgrade to versions 7.2.1 or 8.0.2.
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
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