Package Instance

Puma PROXY Protocol v1 Accepts Repeated Protocol Headers on Persistent Connections
## 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.

## 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

Puma PROXY Protocol v1 Parser Allows Remote Memory Exhaustion
## Impact

PROXY protocol support for Puma was added in version 5.5.0.

When PROXY protocol v1 support is enabled, Puma reads incoming bytes
into an internal buffer. It waits for "\r\n" to determine whether a
PROXY v1 line is present. If an attacker opens a TCP connection and
continuously sends bytes without CRLF, Puma keeps appending to this
pre-parse buffer.

This can cause unbounded in-process memory growth and additional
CPU cost from repeatedly scanning the growing buffer for CRLF.
A single, unauthenticated TCP connection can drive significant memory
growth and may cause process/container OOM or degraded availability.

 Only Puma servers using the following non-default config are affected:

 set_remote_address proxy_protocol: :v1

## Workarounds

* Disable PROXY protocol v1 parsing if it is not required:
  # remove/comment this:
  # set_remote_address proxy_protocol: :v1

* Restrict direct network access to Puma listeners using PROXY protocol:
  * Only allow trusted load balancers/reverse proxies to connect.
  * Block arbitrary client TCP access with firewall/security group rules.